Few things you may want to try:
1. Turn off your phone and turn it back on, this will clear all RAM.
or.
2. Double click home button, hold the app for 3 seconds and hit the red circle with "-" button to remove it from the recently used app tray bar.
or
3. Settings > General > Rest > Reset all Settings.
*Note: this will not erase any data, only resets all the settings on your phone to default
Some people who reported this issue said that #3 fixes their issue with the usage and standby time being the same. If this doesn't fix the problem you have, then you have no choice to restore the phone and go through the process again. I would definitely say go with the Restore and set up as a new phone, not from back up as you may have a corrupted data on your back up.