This article should be helpful.Thanks for reaching out. As you know, I'm not an expert, but I believe the answer is that clocks on the satellites are not synchronized with the ground.
I have not yet ID'ed anyone to weigh-in on this, but am working on it. Maybe there is someone in the forum who could comment?
Here's my summary attempt...
-- Each GPS satellite has an atomic clock.
-- Each satellite is ranged from ground systems to get accurate locations for each.
-- The relativistic time differences are taken into account.
---- The orbital speed of the satellites require SR to calculate how much slower ground clocks run relative to the satellites, which is about 7 seconds per day.
---- Also, the orbital distances of the satellites require GR to calculate how much faster ground clocks run relative to the satellites, which is about 45 seconds per day.
---- So the net is about 38 seconds per day that must be taken into account.