Just a guess, but I think "sanding numbers off the monojects" refers to re-using needles so many times that the ink marking the quantity of liquid in the syringe gets rubbed off. Also, I'm guessing "slight returns" refers to tolerance and not a diminishing supply.
(I used to give liquid medication to my rabbit and I would wash and re-use the same (oral) syringe. The numbers rubbed off pretty quickly.)
Just a guess, but I think "sanding numbers off the monojects" refers to re-using needles so many times that the ink marking the quantity of liquid in the syringe gets rubbed off. Also, I'm guessing "slight returns" refers to tolerance and not a diminishing supply.
(I used to give liquid medication to my rabbit and I would wash and re-use the same (oral) syringe. The numbers rubbed off pretty quickly.)