To enable battery percentage on srt.phone or any Android Nougat devices, do the following:
1) Slide down the drop down notification bar
2) Press and hold the settings icon on the top right cornor for 5 - 10 seconds and release it. Settings will be opened and you will get the following message "Congrats! System UI Tuner has been added to Settings"
3) Scroll down and open "System UI Tuner" setting
4) Select status bar option
5) Scroll down to find "Battery" option. Default setting is "show percentage when charging (default)
6) To show percentage always select "Always show percentage"
Cheers! We will be coming up with more informative tutorials. Stay tuned