Same problem here and everywhere ;-)
The reason is - in my opinion - that lab caches DO count for the counter but DO NOT count for the statistics... (not sure if it's a bug or a feature... perhaps it's just not implemented yet)
n8vision's solution is just one of two - lab caches shouldn't encrease the counter OR should be mentioned in the statistics, otherwise it'll be like Sodom & Gomorrha ;-)
According to the reason why lab caches were implemented I think it should count for statistics, too (except the test labs, because there was no real cache or task like for example a earth cache or something).
Best regards
A