Mm versus millimeter

“Normal sperm count: Over 30 million sperm per mm. Low sperm count: Under 20 million sperm per mm.”

I’d like to make sure if “mm” here stands for millimeter? I find it strange to count sperms this way. :?

Hi … I suspect that the abbreviation should either be ‘ml’ for millilitre, or else should have been preceeded by the ‘word’ cubic. I am not absolutely certain, but I believe that the terms ‘millilitre’ and ‘cubic millimeter’ refer to the same volume.