Do You Trust Krause Mintages Figures?

Unfortunately, you can't, unless you've got access to a local catalogue or an official mint report for that country which might have more reliable mintage figures.

I should also point out that it can just as easily work backwards; perhaps the "old mintage" was correct after all, and the "new mintage" somehow got edited in erroneously.

It may be some comfort to know that such errors are rare, and therefore the probability of the reported mintage of any one given coin being wrong is quite low. However, if you've got thousands of different coins in your collection, the odds are cumulative, and there's a pretty good chance that at least one of them is wrong.

Not that it seems to matter much, as far as determining values is concerned; I'm sure the catalogue prices didn't change at the same time to reflect the perceived change in rarity.