Over the Cap updates it after the NFL awards their picks. They more or less, change their website to make it match the exacts.
When awarding compensatory picks, the NFL uses a formula that accounts for a player’s average salary per year (APY), snap count and postseason awards. The exact specifics of the formula are confidential, but we do know it also takes into consideration a player’s history of playing time (or lack thereof).
What are compensatory draft picks and why do NFL teams get them? - NBC Sports Chicago