Just to be clear - “53 of 50” - what API are you using? Do you mean 53 of 250 (i.e. 30-day search sandbox)?
The period is a month. In the free tier, you get up to 100 Tweets per call, and then 500 per call in the paid tiers. After that you need to wait for the end of the period (billing month) for the counter to reset.