Squarespace 7.0 - Button in Navigation Menu Troubleshooting

Site URL: https://kazoo-chipmunk-khcn.squarespace.com/

I'm looking to add a button to the primary header nav, but it's also appearing below in the folder dropdown menus. Could anyone help me isolate the button to only appear in the main nav and not in any dropdown folders?

This is the 7.0 template, Five, and I'm using the following code:

nav#main-navigation ul li:last-child a {
   background: #000000;
   color: #ffffff !important;
   padding: 10px 20px !important;
   border-radius: 30px;
   border: 2px solid #ffd966;
}

https://kazoo-chipmunk-khcn.squarespace.com/
PW: Sunshine012!

Thank you!

Use this new code

nav#main-navigation>ul>li:last-child a {
    background: #282828;
    color: #fff !important;
    padding: 10px 20px !important;
    border-radius: 30px;
    border: 2px solid red;
}