I’m doing the bridge 3 and i was wondering how am i supposed to calculate the weight to use for my sets.
if my program is :
1@8 (90-93%)
4@8 (84%)
78% of e1rm x 4 sets of 4

I hit the first set and it is 1@8 with 75kg.
Then i calculate my e1rm form that and get 81 kg.
Then i take 84% of my e1rm to do my 4@8,if it feels like an 8 RPE i continue.
I calculate my e1rm again from 4@8 and get 84 kg.
Then i calculate 78% from 84 kg and do the 4x4 sets.

I would look at my previous log and find my last 1ERM. I’d add 1-2.5 kgs to that and pre-calculate 1@8 & 4@8 before hitting the gym.
If the 1@8 isn’t what I planned I’d use a rough calculation to adjust the 4@8. For example if the 1@8 was 100kg and I thought that felt like a 1@6, then i’d take my planned 90kg for 4@8 and move that up to 92.5. If on the first set that was still a 7 then I’d go to 95 for the 2nd set. If it felt like a 9 then I’d come back to 90. I’d finish and calculate my new 1ERM for next time.