(something) is down to (a number of something)

When there used to be more of something, but now there's less of it, you can use the phrase "down to ___".

For example, you can talk about a sports playoff:

They're down to four teams now.

Or about getting rid of things that you own:

We sold the van, so we're down to two vehicles now.

Or about food:

We're down to half a bag of rice.

Usually you say the number of things that you are down to, but you can also list what's left like this:

Now it's down to just me, Brad, and Gbenga.

Notice that it's common to include "now" somewhere in the sentence.