Why multiplication by `4` and division by `10` in `_done` for a progress bar size of `40` in `_left`?

[nooblag]

Hi there,

Thanks for a great little package.

This isn't an issue per-se, but not sure where else to ask the question (sorry). Just wondering why multiplication by 4 and then division by 10 in _done for a progress bar size of 40 in _left?

Can you explain how that part works? Just wanting to understand the maths/what's going on there.

let _done=(${_progress}*4)/10
let _left=40-$_done

Thanks!