Also note that this test isn't totally conclusive; an alarm's power requirements vary greatly depending on what it's doing. For instance, it may have enough power to chug along for another 24 hours in standby, but during a break-in when it tries running the modem and sirens, the voltage requirements spike and it just might crap out before it ever does its job.
It's a good idea to look at everything connected to your M1 and pay attention to the rated current draw and also compare that to actual current draw in standby and during alarm - and calculate what you expect to get out of the system by comparing the loads to the battery's rated power.
There's no simple answer to the question so do the math and over-engineer a little bit for your goals.