Gap between nav bar and submenu

I’m running twentyten (using a slightly modified child theme). I reduced the height of the main nav bar from 38px to 30px, which I thought looked cleaner. Problem is that now there is a gap between the nav bar and the sub menu box so you cannot access the sub menu at all because your cursor leaves the nav bar, hits empty space, and makes the sub menu disappear! I haven’t a clue how to fix this. I tried increasing padding in the submenu, which not only looks ridiculous but didn’t work to get rid of that gap anyhow. (I put that padding back to default.)

How can I keep the nav bar at 30 px but not have that gap?

I’m new to CSS – so if you could tell me exactly what I need to change or add and where to put it, I’d really appreciate it! Thanks so much.

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