joker, my Original Surface Pro with Windows 8.1 < usually > shows me both hours and minutes and percentage left.
For some unknown reason, at times it only shows the percentage.
Why, I've no idea. It just seems to do whatever the hell it wants.
Every morning I use my Surface and then open a spreadsheet where I record how much time is left and it calculates how long the full charge would last at the percentage given.
That answer varies all over the place from something over an hour to over 5 hours.
No rhyme or reason to it.
It appears the battery app is WILDLY inaccurate and pretty much useless.
My Surface shuts itself off automatically at about 6% left anyway.
It won't even LET me drain it down to nothing.