The Homunculus is described as a Challenge Rating (CR) 0 creature with 5 hit points and a poison attack that, if PCs fail a DC 10 Con save by 5 or more, causes unconsciousness for 1d10 minutes.
According to the "Challenge" section in the intro of the MM (p. 9):
A monster's challenge rating tells you how great a threat the monster is. An appropriately equipped and well-rested party of four adventurers should be able to defeat a monster that has a challenge rating equal to its level without suffering any deaths. For example, a party of four 3rd-level characters should find a monster with a challenge rating of 3 to be a worthy challenge, but not a deadly one.
As we understand it, a CR1 creatures is considered an even match for four level 1 PCs. A CR 1/8 creature would need eight creatures to be an even match for level 1 PCs.
That math doesn’t seem to work out for CR0 creatures as it seems to imply an infinite number of creatures would be required to create an even match.
How does one calculate an even match with CR0 creatures? Given the Homunculus’s rather powerful poison attack, how many Homunculi would be an even match for a party of Level 1 PCs?