Setting up single limit protection for an address means that this particular address will be able to transfer not more than a given number of tokens in a set period of time. For example, an address has a limit of 100 000 tokens per hour. Token transfer transactions will start failing if that address transfers out more than 100 000 tokens in an hour. However, the limit gets reset every period. Therefore, even if transactions start failing or the amount transferred is close to the limit, this only lasts until a new period is entered. In the previous example, this would mean that once one hour passes, the protected address can once again transfer up to 100 000 tokens.