Usually the AC system will have a refrigerant pressure switch that prevents the compressor clutch from engaging if the pressure gets too low. This prevents the compressor from being damaged in case of refrigerant loss.
No way to tell how much refrigerant you lost. Just retighten the bolt and keep driving. As long as the compressor runs and cold air is coming out if the vents, the system is working. When the refrigerant eventually leaks out (as it always does, slowly, over years) the compressor clutch will stop engaging and you won’t get any cold air. Then you will need to refill the refrigerant. If you’re lucky you still have a few years left.