Our keyboards do not support the battery percentage feature on macOS similar to the Apple Magic Keyboard or Mouse.

Even if the keyboard is fully charged, macOS will not reflect that because our keyboard does not support this feature. (in most cases it will display around 60% even if the keyboard is fully charged).

Our keyboard actually notifies you it is low on battery with the power LED indicator found at the top right:

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The LED light will blink red when it has reached below 15%. 

We recommend charging the keyboard for at least 3-4 hours for a full charge.