This has been discussed so many times and, of course, the "last update" doesn't have anything to do with this.
What do you mean with "I have 50 passengers" ? In the airplane own loading page or FMC ? If yes, that doesn't mean anything to GSX, unless the airplane is specifically programmed to communicate with GSX its own passenger number.
If the airplane is not specifically programmed to interface with GSX to send the passenger number (which is a concept that doesn't exists in the simulator), the passenger number will be estimated by GSX, depending how you set the "Estimate Passenger Number" option in the GSX Settings.
- If you have it Enabled (which is the default), GSX will estimate the passenger number based on the actual Payload, so it will be up to you to set it correctly BEFORE calling GSX
- If you Disabled it, GSX will ASK you every time how many passengers you have, and will use that number to decide the kind of bus to use.
However, if your airplane interfaces with GSX, the number is handled by the airplane code itself. You don't say which airplane you used, so it's difficult to know if this could be your case.