Match the Scroll-top Position to header-scrolled height

Hello!

I love this theme. I have ran my online store with it for years and wanted to redesign my store. Recently I purchased the “Divi Theme”, went right back to Enfold and got my refund! :)

My question has to do with making the scrolled-header active when it matches the new height I’ve given it. The regular navbar height is 77px and I have change 50% of the height to (75% ?) :
if(st < el_height/1.5)
newH = el_height/1.5;

So ideally the scrolled-header would be activated when scrolled about 13px from the top of the page.
Would someone be able to help me with this?

Thanks!