Averaging works like this. For simplicity I just mention qualifying by sectors but the same logic applies for qualifying by miles.
If since first qualifying for PPS have on average more than 25 PPS sectors per year, and in the requalification period have more than half the annual requirement (ie at least 12.5 PPS sectors), then may requalify by averaging without getting the 25 PPS sectors in this year. However, will only be assessed for requalifying early at about 3 months out from your requalification date.
Example
first PPS year get 35
second get 25
then to requalify need 75 total (3 * 25), and minimum of 12.5 = 15
but if in second year get 35, then to requalify need 75 total and minimum of 12.5 = 12.5
Please not averaging is not a published benefit, so could be removed as a method for requalifying at any time.