I would expect that they may have had 40M in December/January, and it is possible that they are using those numbers. 40M sounds high to me, but it is possible.
You should also be wary of the fact that they can't tell you how many searches there were for the phrase(s) that you want in March. As a general rule on the web, unless I know the numbers, I won't buy it.
Out of 5, two are performing REALLY well - the others (due to ToxicLemon, DogPile and RedHotChilli all dropping in the SERPS) not so - however this reseller offer a guarantee of positions for terms for first month or money back....
If you can get big terms along the lines of estate agents (Over 1 million search terms) or good terms like secured loans (small volume but high conversion potential affiliate-wise) then it is worth trying out - IMHO