Changing size of custom font on navigation - 7.1

Site URL: https://vanilla-sunflower-m9gz.squarespace.com/config/design

I have added a custom font to my 7.1 SquareSpace site but the font is too big for the header navigation. How can I make the font smaller? I have tried to add the following code, as found on another forum thread, but it hasn't made any difference.

 .header-nav-item a {
    font-size: 10px;

Thanks in advance.

Your site is private. Your code should work for 7.1, you are missing the }

You should also use em and not px, you could try this as well.

.header-nav a {
    font-size: .8em;
}

If you set your site up for password access, I can find out the correct code if these dont work.

edit your code to

.header-nav-item a {
    font-size: 10px !important;
}

Thank you rwp and tuanphan,  I changed to em as receommended and that has worked. Thanks for your help!