I believe that is a changeable parameter in AMO DIMSU. Apparently it was set low, and you have now met that maximum-supported number.
DIS-DIMSU -> ALL and locate "CALLOG". You should be able to see if the max number has been reached. If so, then perform:
ADD-DIMSU, then locate the "branch" of DIMSU where the "CALLOG" parameter is maintained, then increase the number GENTLY.
Do not make it some exorbitant number, but rather increase it by perhaps "50".
I typically do not work with stations, so if I am wrong on this - sorry in advance. But I do recall encountering this same situation many years ago.
Good luck.