Well my guess is; it's probably the number of files in that particular zip folder being unzipped. Or the number of files being installed in total. Why would you want to know anyways?
Peace is that brief glorious moment in history when everybody stands around reloading
When you update a file in a zip archive (even if it's just one file), all entries must be re-saved. That is the progress when saving the archive (current file/total files in the archive).
The 1st row of numbers show the percentage of the file being unzipped and saved, while the second row shows the total number of files completely installed and the remaining amount.