Hi NoelGustafsson,
Thanks for reaching out to Microsoft Community and posting your inquiry.
Based on the details you have provided, this functions on the F1 to F7 keyboard for Surface Book 3 are correct. Please check on the picture provided below:
In Surface Book 3, F6 lowers down the screen brightness and the F7 will make the screen brighter. F1 is for the keyboard backlight adjustment.
May we ask for a clear photo of your keyboard?