what do you mean by syslog capacity, how many Events per second an MAG2600 or MAG4610 can shoot out?
Or do you mean how many log messages can localy stored?
Thank you for providing more information.
there is no limit to how many syslog servers you can configure; however, as NULL pointed out, it is not clear the question you are looking to know.
the on-board storage limit is 500MB (compressed on the system)