Different high schools in the US have wildly different ways to calculate GPA, and the admissions staff know this. Colleges and universities will see your actual grades. Many recalculate based on their scale (which is probably slightly different from your high school and also different from the high school in my town).
Agree with the above. In addition, your HS will send a school profile that among other things describes the grading scale at your HS so your transcript will be review in the proper context.
It’s not weird. There is no standard weighting scale for HS’s. For that reason, colleges will concentrate on UW GPA, or will reweight according to their own standards. As also mentioned, schools will send a school profile which explains their grading policies.