I may be wrong, but isn't this computation implicitly assuming that 0% of all Republicans in PA voted for Biden? Otherwise, you're not really getting any meaningful information by dividing the total number of absentee ballots that voted for Biden (Dem + Ind + Rep) by the total number of absentee ballots submitted by only Dems and Ind.
To get the actual % that you're looking for, you'd have to first subtract the percentage of republicans that voted Biden from your first number (getting the percentage of Dem + Ind Biden voters rather than Dem+Ind+Rep Biden voters), and then divide by 77.2%.
Here guys, my wife updated you all with some more context into how she got these numbers:
PENNSYLVANIA
% of Absentee Ballots that were Returned from Registered Democrats and Non-Republicans:
Democrat Absentee: 1,600,00
Independent Absentee: 278,000
Republican Absentee: 586,000
(1,600,000 + 278,000 ) / (1,600,000 + 586,000 + 278,000) = 0.7622 = 76.22%
(https://www.politico.com/news/2020/11/03/democrats-more-mail-in-ballots-pennsylvania-433951)
% of Absentee Ballots that voted for Biden:
Total Biden Mail Votes: 1,921,185
Total Trump Mail Votes: 575,774
Total Jo Mail Votes: 23,707
1,921,185 / (1,921,185 + 575,774 + 23707) = 0.7622 = 76.22%
(https://electionreturns.pa.gov/)
% of Democrat and Non-Republican Absentee Voters who voted for Joe Biden:
76.22% / 76.22% = 100% (or 99.53% if you use the numbers from the picture)
NORTH CAROLINA
% of Absentee Ballots that were Returned from Registered Democrats and Non-Republicans
37.34% Absentee were Democrats
31.68% Absentee were Republican
30.99% Absentee were Other
37.34% + 30.99% = 68.33% (Oops. Good thing you guys asked for this proof!)
(https://dl.ncsbe.gov/Press/NC%20Absentee%20Stats%20for%202020%20General%20Election/Absentee_Stats_2020General_11042020.pdf).
% of Absentee Ballots that voted for Biden
51.7% of North Carolina absentee votes went to Biden.
(https://www.nytimes.com/interactive/2020/11/03/us/elections/results-north-carolina-president.html)
ARIZONA
% of Absentee Ballots that were Returned from Registered Democrats and Non-Republicans
36.5% Absentee were Democrats
37.4% Absentee were Republican
26.0% Absentee were Other
(https://www.dataorbital.com/2020-general-election-early-vote-tracker). 36.5% + 26.0% = 62.5%
% of Absentee Ballots that voted for Biden
52.1% of Arizona absentee votes went to Biden.
(https://www.nytimes.com/interactive/2020/11/03/us/elections/results-arizona-president.html)
FLORIDA
% of Absentee Ballots that were Returned from Registered Democrats and Non-Republicans
Democrat Absentee: 2,189,517
Republican Absentee: 1,506,744
Other Absentee: 66,280
No Party: 1,092,941
(2,189,517 + 66,280 + 1,092,941) / (2,189,517 + 66,280 + 1,092,941 + 1,506,744) = 0.6897 = 68.97% (Oops. The difference still stands.)
(https://countyballotfiles.floridados.gov/VoteByMailEarlyVotingReports/PublicStats)
% of Absentee Ballots that voted for Biden
50.2% of absentee votes went to Biden
(https://www.nytimes.com/interactive/2020/11/03/us/elections/results-florida-president.html)
CALIFORNIA
% of Absentee Ballots that were Returned from Registered Democrats and Non-Republicans
With this site you can request data from California (https://docs.google.com/forms/d/e/1FAIpQLSfipraqZymaSWDDYjVkidhZ0fpvHGpLuALrX9FxSr0JKeIDGw/viewform). I didn’t have all day so I found a guy who did! According to https://electproject.github.io/Early-Vote-2020G/CA.html,
50.9% Absentee were Democrats
24.4% Absentee were Republican
24.6% Absentee were Other
50.9% + 24.6% = 75.5% (Another discrepancy. I was tired when compiling data.)
% of Absentee Ballots that voted for Biden
According to the New York Times,
(https://www.nytimes.com/interactive/2020/11/03/us/elections/results-california-president.html)
68.1% of absentee votes went to Biden.
I may be wrong, but isn't this computation implicitly assuming that 0% of all Republicans in PA voted for Biden? Otherwise, you're not really getting any meaningful information by dividing the total number of absentee ballots that voted for Biden (Dem + Ind + Rep) by the total number of absentee ballots submitted by only Dems and Ind.
To get the actual % that you're looking for, you'd have to first subtract the percentage of republicans that voted Biden from your first number (getting the percentage of Dem + Ind Biden voters rather than Dem+Ind+Rep Biden voters), and then divide by 77.2%.