There is no limit on the amount you can cash out per month with ZIPZERO. The figure of up to £10 per month for previously accumulated Base units detailed in the email, is an additional payment that finally allows you to unlock your historic units, once the change is brought in.
For example, if you have £30 in old Base units (units acquired before the changes to the app come in), you will be able to cash out these funds at a rate of £10 per month, starting on the 1st day of the subsequent month. Please remember, these funds are separate to any Premium units or new Base units you have available or pending. Once Premium or new Base units become available, you will then be able to use these on top of the £10 in old Base units that will be unlocked each month.