The numbers are on Olfa Blades. Here's the explanation from the olfa site,
https://www.olfa.com/faqs-olfa.html
08. What do the numbers around the perimeter of the rotary blades mean?The original rotary blade was designed to fit a safety cutter that positioned each section of the rotary blade in a fixed position to be used upon the dulling of the previous section. The numbers represented each of those sections. When OLFA introduced the original rotary cutter in 1979, the numbers became irrelevant, but have been maintained as a sort of historical feature representing the original rotary blade.