How to reduce top and bottom of header nav on DeGraw

Site URL: https://holisticbirthandyoga.squarespace.com/

Hi there, 

Wondering how I reduce the size of the top and bottom of my header on Degraw template? I'm able to do the top but not the bottom. The site URL is https://holisticbirthandyoga.squarespace.com/ and the password is 'mindbodyseva'.

Here is my code: 

 #header {
 margin-top: -10px !important;
}

Thanks!