For making this cleared, your billing cycle will be counted as 30 days. (From the day of your approve charge processing)
Within 30 days, you can uninstall and re-install our app several times without being double charge or multiple charges on your billing payment. (Just approve the charge and you won't be billed twice)
As long as it's still in your 30 days of billing cycle.
After 30 days of your billing cycle, you have re-installed our app and approved the charge again, it will be counted as the new billing and started your new billing cycle on the day you have clicked on the button "Approve Charge"
And yes, you will be charged for new billing invoice with this situation.
*NOTE: so please help me to make sure you are going to reinstall our app within 30 days of your billing cycle to avoid this double payment.
I hope this might be helpful for you, please contact to us via chatbox for more information if you are still concerning about this case.
Should you need further support, please feel free to contact us via live chat or email us at firstname.lastname@example.org