You understand it if you think of engineering infinites rather than mathematical infinites. The capacity of a full single datacenter can be treated as infinite for most customers. I explained how its defined in the original comment. Amount of places in engineering where you treat even a 3 order of magnitude difference as infinite is a lot, but the number of order of magnitudes varies depending on context.
You don't have a single Google datacenter (or any other provider / big name) for a single tenant. The bigger the DC, the more the number of tenants/customers reaches "infinity" (giving the same meaning to "infinity" you are giving to it)
