I spoke to one of the guards about it the other day when I was in for the first time. He said the sign had been mentioned by more then a few people regarding the wording and he agreed it wasn't clear. He did say he generally didn't stop anyone from OCing as long as the handgun was secured in a holster but store management didn't want anyone OCing long guns coming in. You'll be asked to leave it in your vehicle unless you have a reason for bring it in. It will be inspected and unloaded before they allow it to pass. They do want to inspect any firearm which comes in that will be handled openly in store by guests or staff.. mostly to ensure they are unloaded.
Was back in that area today and stopped in again to pickup a new Tilley Hat for myself and a new youth camping chair for my son. I noticed 2 separate individuals OCing a handgun inside the store.