Yes, like someone about to commite grand theft and armed robbery is going to care about the sign. NOT! Mr. Komara has just put his employees in greater danger than they were before, wether THEY are allowed to be armed or not. Because as we all know: so called "Gun Free Zones" are really "Unarmed Victim Zones".
Playing devil's advocate here, but if the employees are armed, I can see that there could be some problems or confusion in the event that any armed citizens interceded to try to stop a robbery. If a store clerk sounds an alarm and someone in the back room comes in with a gun, it's not hard to imagine that he might misidentify as a criminal a concealed-carry holder who was trying to help.
That having been said, if the owners are concerned that they might miread the intentions of concealed-carry holders, perhaps they might instead put up a sign asking that all concealed-carry licensees keep their firearms concealed, and that anyone brandishing a weapon in the store may be regarded as a deadly threat and treated accordingly.