AS:CE, p. 143 appears (to me) to imply that a unit can carry one type of alternate ammo in addition to standard ammo, but doesn't explicitly state such. I've tended toward checking the BT record sheets and going by the number of ammo bins as per TW rules, but that isn't necessarily an option for AS-only players.
So, I feel the need to ask here, before posting in rules questions: How many types of ammunition, including standard, can one unit carry?