It has been proven that activating a hack that enables the numeric percentage battery display on iPhone causes the battery to be drained much faster.

Some people thought that it was just a psychological effect, because seeing a number going down instead of a bar, makes you think that the battery is discharged faster. So they thought that the discharge time is actually the same. But it is wrong.

Definitely displaying a numeric percentage makes the iPhone consume much more battery power. Apple has a reason that they did not enable this feature. So, keep it disabled.