Are you in the USA?
USA matches have different rules than the rest of the IPSC world.
Unless the match you attend is specifically run under IPSC rules, USPSA rules are followed.
But either way, do you really care, for your first match?
The worst that can happen is you will be put in the Open class.
No harm, just enjoy the match.
Just be sure your holster covers the trigger guard and securely holds the gun.
And definitely read the rules beforehand so you don't get disqualified for something.
Lock the doors, they're coming in the windows.