What causes this error message "not enough data storage to research [x]" when using the stock lab?

[BudgetHedgehog]

Posting here because while I think it may be a stock issue, one of the mods may be causing it (also, I'm aware I'm using the KSPWin64 hack, so feel free to ignore/delete this, though I'd really appreciate some advice).

Science Revisited Revisited boosts the labs data capacity from 500 to 1500, so with roughly 739 data already, you'd think I'd have plenty of room for an extra 144, right? Well, it got added, but the warning still appeared. Is it like, hardcoded to appear over 500? That said, I think I remember it appearing when I was below that as well..

Windows KSP 1.0.4 (obviously) 64bit workaround, OS Win64, all the mods

[Stoney3K]

This also happens in stock x32. The data is stored and the science is processed, the only annoying thing is this message which makes no sense.