OBJ signed a 1 year, $4.25M contract with the Rams.
$750K of that is salary and another $500K is a signing bonus, a total of $1.25M which goes against this year's cap.
The remaining $3M is incentives.
$500K if the Rams win the Wild Card game (which he would have also gotten if the Rams had the bye).
$750K if the Rams win the Division game
$750K if the Rams win the NFCCG
$1M if the Rams win the Super Bowl. (He will get $500,000 if he is active for the game and the Rams lose).
When the NFL evaluated the contract those bonuses were considered Not Likely To Be Earned (NLTBE) so they did not count against this year's cap.
As things turned out he will collect either $2.5M or $3M in bonuses. The Rams pay OBJ as they are earned and they will count against their 2022 cap.
If he had any of the 'other' kind of incentive - Likely To Be Earned (LTBE) - they would have been counted against this year's cap. For example, if he had an incentive that paid him $1M for catching at least one pass this year I'm pretty sure the NFL would consider that LTBE and it would have counted against the cap as soon as OBJ signed the contract. Then, if he didn't actually catch a pass with the Rams the team would have had $1M added to the 2022 cap.
AlbaNY_Ram