ibackupbot seems to round to the nearest 100mAh nowadays on iOS 10.So it rounds by the hundredth? (And thanks)
I believe your batteries capacity is close to 1950mAh and with slight fluctuations it is rounding it to either 1900 or 2000 depending on whether it's slightly above or below 1950mAh at the time it reads it.
My iPhone 7 shows a constant 2000mAh on ibackupbot, so is consistently above 1950mAh at the moment.
Cheers