Exaggeration only works if the numbers you are using are ridiculously out of keeping with those of reality. In this case it didn't work because ADWD is expected to have about 50-60 chapters in it total (divided between 11 POV characters), so saying you have 38 chapters to wrap up seemed plausible, if a bit worrying if you're trying to finish it in the next two months.

Luckily, he did confirm that that was an exaggeration and a number he plucked out of thin air.