[Pibwl]

...supplement: there was also an ammunition box with 6 rounds on the upper carriage.
"Encyclopedia Of German Tanks Of WWII" by Jentz & Doyle claims, that it carried 40 rounds, but Panzertracts are much more detailed (Encyclopedia also gives a crew of 9, but documents quoted in Panzertracts state it was only 4 - there was 9 in a version towed by an armoured tractor).