Quick CSS Code Working On All Websites Except One

Hi,

We have been customizing the spacing on Main Menu elements using this code: https://kriesi.at/support/topic/placing-menu-below-header/#post-286722 for all three of our websites. Two of them work fine it seems, but for some reason, there seems to be an issue with one of the websites. If I make padding space 9 or “0 09” pixels, it squashes the menu headings together. But if I make it 10 or “0 10” pixels, it spreads significantly and pushes the headings out so far it spills over into another row. It seems that these are the only two extremes, no other higher or lower amount causes any slight changes. Links and example have been pasted into examples section.

The bit of code applicable to this issue and browser is:
@media only screen and (min-width: 1140px) {
.av-main-nav > li > a { padding: 0 10px; }}