The update that you received is a maitenance update of Gingerbread OS (OTA only). You need that update to proceed to Android 4.03 ICS thru KIES ONLY.
Kindly read this
The notification you are seeing is a maintenance update as colt149 said. The phone will eventually force the update, if you do not accept it. The update to ICS is optional, and is only available through the Samsung Kies software.