What Gives With Bogus Google Web Page Counts?

It seems Google's web page count is giving spurious counts.

I was surprised that when searching the word throatwash Google only showed there being 67 web pages for it:

"Results 1 - 67 of 67 English pages for +throatwash"

But Adding another search term (which should reduce the hit count) increased the number of results:

Results 1 - 100 of about 958 English pages for +throatwash +three.

I can understand that not preceding a search term with a "+" sign will give more results, since Google also adds variants like "throat wash" to the search:

"Results 1 - 100 of about 1,650 English pages for throatwash"

Any explanations?

In any case, considering how many web pages Google indexes, throatwash produces a surprizingly small number of hits.