Rechargeable Boosters let you recover and reuse items, to help you power through challenges.
Normally, when you play the last of any Booster, it'll slowly recharge from 0 to 1 over time. But when you win this 'recharge Booster', the recharge is immediate.
For a Booster to recharge, it must have been completely used up, so the balance must be 0. This allows the Booster to be recharged, so you can use it again.
Recharges only happen between 0 and 1 Booster quantity.
So you'll see the increase:
1 - If you've used the Booster in your attempt at the level where the reward is shown
2 - If you've used the Booster to 0, so it can then recharge to 1
We do offer extra Boosters at the end of events and in some different prize packages, but these are not labeled 'recharge' and so can be added regardless of the above two conditions.