...and if no person have such majority, then from the persons having the highest numbers not exceeding three on the list of those voted for as President, the House of Representatives shall choose immediately, by ballot, the President. But in choosing the President, the votes shall be taken by states, the representation from each state having one vote

Biden as it stands has majority, and so they would have to contest the votes that go towards his majority first. That objection is accepted if both chambers of congress agree by majority. If all objections are realised then he has no majority, no one has majority, then it goes to 1 vote per state delegation.

https://chb44.com/2020/12/us-presidential-miracle-still-possible-donald-trump/

EDIT: Should clarify, I wonder if it's a possibility that Pence will outright reject to count the votes himself, because then we're on.

...and if no person have such majority, then from the persons having the highest numbers not exceeding three on the list of those voted for as President, the House of Representatives shall choose immediately, by ballot, the President. But in choosing the President, the votes shall be taken by states, the representation from each state having one vote

Biden as it stands has majority, and so they would have to contest the votes that go towards his majority first. That objection is accepted if both chambers of congress agree by majority. If all objections are realised then he has no majority, no one has majority, then it goes to 1 vote per state delegation.

https://chb44.com/2020/12/us-presidential-miracle-still-possible-donald-trump/