Colour Widgets Battery Inaccurate

In the app Colour Widgets, you have the option of making a battery % widget that looks cool; this would be well and fine if the widget actually showed the right battery percentage, which half the time it doesn’t, often being off by about 5% (though while the phone is charging, it has even been off by 30+). Anyone else have this issue, or any recommendations on how to fix it? Thanks