Xbox Live Gold Converting to Ultimate Game Pass

I currently have an Xbox Game Pass Ultimate subscription active on my account. I want to purchase an additional 12 months of Xbox Live Gold. I have about 1 month left on my Game Pass subscription. If I purchase an Xbox Live Gold subscription while the Game
Pass is still active will the amount of time of Gold that I purchased be less due to it converting to Ultimate or will I then have 13 months of Xbox Live? Gold. Note: I have never converted my Xbox Live Membership into Game Pass as Game Pass is my only subscription
ever. Please help.

Thanks!

:)