"N.OFF is the amount of points that will be coming off your rank the next week. 11th tournament is your 11th best tournament that will replace one of your top 10 if they are dropped."
I am new to this so please can you explain this in a little more detail as I don't understand, sorry
The FITD ranking works similar to the ATP ones. It is the accumulation of points from 12 months (1 full year). Each week, the points from the corresponding week of the previous year will be "dropped" and replaced with the points earned in the current year.
For example, this week are the Memphis, Marseille, and Buenos Aires tournaments. During this same week last year, the tournaments Dubai, Acapulco, and Delray Beach were played and these points earned last year will be taken away from the rankings on Monday. They will be replaced by the points earned in the 3 tournaments this week.
The "Next Off" column is basically letting you know the amount of points that will be dropping from your ranking in the following week.
Hope this makes sense!