Of course. This needs "in" not "at". I've edited it here but must change the incubator which seems to be stuck. If you remember which unit you found it in I will be able to make the change. Many thanks.
Hope you're not afraid of ghosts because you just got a ghost sentence. I'm assuming this was on Strengthen skills which has been known to have these issues. This sentence was deleted a long time ago but pops up now and again on Strengthen skill.