Gamertags with numbers first.

No you get to keep your gamertag but if you change it in the future it will only have the numbers at the end if someone else also has the same name but if you're the first then it won't have it but the other person will have the numbers at the end showing
they aren't the first to have the gamertag

Thank you, I ask this because when you have numbers after the # symbol. For the system it means that your have the OzzyKP gamertag.

In order to change OzzyKP5721 to the one without numbers, you may need to change first that gamertag to a completely different gamertag, for example, change OzzyKP5721 to OzzyKKPP and then check if OzzyKP without the numbers appears

PS: But keep in mind that this doesn't guaranteed that you're going to see the gamertag without the numbers available

This account which i used to change the Gamertag. It had the tag of “SvmmyTvlhvMCYT” it didn’t have the numbers. I created a new account it didn’t had any numbers. I used another account to change an Gamertag (after the first account) it didn’t show any numbers.

The new gamertag system is still rolling out. Some games will show the numbers while others will not. For the time being, the numbers will be visible and part of the gamertag.

The only way to get a tag without numbers is to be the first person to have the gamertag.

More information on the new gamertag system and the transition time of games over to it can be found at https://beta.support.xbox.com/help/account-profile/profile/gamertag-update-faq

Just figured it out last time my friend checked both the gamertags first and he wasn't getting numbers and I was but today I checked it first and I did not get any numbers but he did so my guess is that if someone recently checked a gamertag it reserves
the one without a number for them in case they end up taking that tag, so there that's the only reasonable explanation I can come up with for this.