Sorry for not weighing in here earlier (sometimes days go by without me logging in when I'm heads-down designing).
The AP2E time is measured between the end of the ejection shock and apogee, or vice-versa. Much of the time when you eject on the way up, the rocket kind of "grinds to a halt". What the altimeter senses is the ejection shock and then some buffeting, spring-back, and even tumbling-- then the apogee. It usually happens rather close together, and times are rounded to the nearest tenth in the display (even though they are sampled every 1/244 of a second). Typically, you don't see very big numbers here, because if you've got a healthy ejection shock, stuff is going to stop rising pretty quickly. Often, not always.
If you're worried it's not working correctly, you can simulate a launch a by shaking (launch), sucking (in cupped hands or a bottle), shaking(ejection), set on floor (landing lower down). The speed values will be wacky, but the timing ones should be reasonable.
Help any?