that's normal for most of the Mobile Phone...
it's dipend how you use it!
If you spend your 3.15 hours... using internet, wi-fi and Display ON for most of the 3 hours...
that's normal...
if you condider that in conversation the minimus endurance of your mobile reported into the official descriptions is 360 minutes (6 hours)...
consider that browsing into internet, cosume as a phone call and more, because you have got also the Display On...
3.15 hours at 60% can be normal... or maybe more than expected...