unsure of battery life calculation

I'm trying to calculate the life of a battery:

duty cycle: 3%
current drawn during activity: 1.53 mA
current drawn during inactivity: negligible
transmission time: 33 ms
battery capacity: 2510 mAh

here are my calculations, but I could be wrong here:

Battery capacity: 2510 mAh
Current drawn in 1 hour = (1.53 mA / 3%) x 100%
Current drawn in 1 hour = 51 mA
Battery life in seconds = ((2510 mAh / 51 mA) x 60 minutes) x 60 seconds
Battery life in seconds = 177176.47 seconds
Battery life in seconds = 1.77 x 10^5 seconds (3sf)

any advice would be appreciated, as I really want to get a clear understanding of this calculation, + the tuition I received was inadequate. thanks