I don't see my full amount of data

Hello,

I very recently got the 15GB data plan, and this is my first time having data. When I checked the usage tab to see if I can start using the data, it says 0/6.5GB. My bill cycle is July 11-August 10, and I switched my plan July 30. Is it not showing the full 15GB because it’s still between the cycles/It will show the full amount by August 11? If so, am I still ok to use the 6.5GB of data?

Thanks in advance!