The phrase
"multiple hamsters" means having more than one hamster at the same time.
Full definition
If you have
multiple hamsters in one cage, you will likely need to fully clean the enclosure twice weekly.
Thus, if you
own multiple hamsters, you will need to prepare a different cage for each hamster before they are 2 - 3 months old.
As you might think, urine and waste can create an unpleasant odor, requiring you to change your hamster bedding once a week and in hamster cages
with multiple hamsters, more often than that.