We definitely need to get that fixed as you're not the first one to ask us this question.
The space was limited on the label so we couldn't fully explain, but we definitely could've done a better job.
You can use this product both indoors and outdoors.
What we tried to say was, don't use it outside in the sun if the surface is super hot.
If you are using outdoors in the sun, the surface temperature should be at maximum, warm to the touch
(you should be able to comfortably hold your hands against your paint).
The optimal place to use it would be inside your garage, in the shade, on a cool surface.
But if that isn't an option, an easy way to determine if it's okay to use is to make sure you can comfortably hold your hand on your paint.