As the name implies, these are the scores given to you on a specific Category in the last 30 or 60 natural days.
Keep in mind that these scores can change a lot from one day to the next depending on when a particularly good or bad score was given.
For example if today is April 30th the 30-Day Index will take all the scores given from April 1st until today. So, if on April 1st someone scored you with a particularly low number, your 30-Day Index will show that.
However, on May 1st, the average will no longer take April 1st into account but rather begin from April 2nd.
The same applies for the 60-Day Index.