You have her number...she gave it to you. You have enough value to her that she gave you her number.
Would you guys stop trying to 'game' every female. I think you should call...which sounds like it'd be easier on you than building up your value with her one-on-one. Just saying.
I think that often beautiful girls aren't approached as much as you think they are...because they're so beautiful. She gave you her number because she wants you to call. I think you need to do that soon. If you see her again in a few days at the gym and haven't called, you're telling her you're not that interested in her...or 'weak.'
Should I write an entire script for you? Oh, btw, don't do what another fanatic did and text her a photo of your penor...although it worked out great for that fanatic, ymmv!