How to fine-tune the modal window in uikit 3?

Question

UIkit

Task:
There is a modal window that should pop up from the bottom up, full screen wide, if there is a lot of content, then full screen height with the appearance of a vertical scroll bar in the modal window itself.
For an hour I tried to implement something like this and this is what happened https://jsfiddle.net/qoewj3nf/
Everything would be fine, only when the window pops up, there is a small gap on top, and I need the indent from the top edge to the module window myself could control. For example, I want this padding to be only 10px.