Number in in parentheses after my name at bottom of page under Apple ID iPhone.

To remove the number in parentheses:

Go to Settings, and press on your name at top of page.

On next screen at the bottom, under Family Sharing, it shows devices you have or had in the past that are connected or synced.

Tap on one of those devices that are shown under your name, but do not tap on the first one that shows your name.

It will go to a new screen and give you an option to delete that device.

Delete that device and when you go back to the previous page it will have removed the parentheses with the number.

You can then re-sync the device you deleted if you need to.