It's the same number all RR teams have available.
If you look at the number of mortar rounds are provided to mortar teams you might wonder how 8 men could hump 100 81mm Mortar shells and two mortars from place to place as well.
It's one of those little compromises between game play and "realism" that we get beaten up for once in awhile. Yes, we know it's a stretch to think of 6 men carrying 10 rounds of 106mm ammo each, plus the tube and tripod but the number of rounds these units carry were hashed out quite some time ago in playtesting and it was agreed that although we tend to give to much it makes the game more playable ( which sends the "realism" crowd into a tizzy but I'm not thinking of you per se so please, don't take offense
)
Don