Hi @noureddine.bassa ,
Since we assign 1 to pixels which meet the condition and 0 to pixels which don’t, you can imagine that we are counting the number of pixels meeting the condition when calculates the mean. In your case, we plus 1 when there’s a pixel greater than or equal to 0.8 and we plus 0 if the value is less than 0.8. At the end, by dividing the total number of pixels within the AOI, the mean value will be the percentage of pixels that meets the condition.