Your stats are totally messed up. Reset your phone may help.
I reset my phone Friday before I did that battery test I posted, I also reset the phone again today.
Interestingly, my usage time that I had posted above was about 28% of standby for the first 25 hours off the charger, which is pretty typical of any iPhone that isn't touched much and is otherwise just doing it own thing, except for a couple of phone calls.
But then I started to use it more that day to read a book for 3.5 hours at the end of the day, and usage time jumped to about 40% of standby in the last 10 hours. However, that 3.5 hours of eBook reading resulting in a 7 hour climb in usage. So I agree, at the end, the usage climbed faster than it should have.
One day I used the phone non-stop over 10 hours off the charger, and my 8 hours of recorded usage was about 80% of standby time, but usually it seems that I can use the phone continuously for 8-10 hours with very little standby before I kill the battery. I'm sure with gaming and a bright screen I could kill it in about 6 hours.
Today, I used my phone a bit more than I did over the weekend, with Kindle, Phone, Safari, Messages, Mail, etc, and I still got 9h:7m usage with 14h:40m standby and 25% remaining.
Of that 9h:7m usage, I really did use the iPhone screen for about 5 of those hours (note - in the "last 24 hours" usage time/% estimate screenshot below, a lot of the last 24 hours was while I was asleep from 2AM to 10AM, then I had it unplugged for 14 hours from 10AM - 2AM before posting this).
If I could stay awake I could get another 3 hours of usage over 20 hours of standby, I think.