If you invite me to your home for 6:00 I will arrive at 6:00.
Don't assume that I'll take that to mean 6:15 or 6:30.
If you want me to arrive at 6:15 tell me to arrive at 6:15.

And don't give me the "around six" or "sixish" nonsense.
Do that and I'll still arrive at 6:00.

Say what you mean.