On the Kodak film pack after you have made your exposure you pull the tab out as far as it will come. You can then either tear the tab off or leave it attached. So I would expect that if the number 12 is showing then 12 exposures have been made - most Kodak film packs held up to 16 exposures. From the pictures you posted it looked like three exposures had been made and No. 4 was ready to be used.
When processing a sheet you should develop the first one in a tray. I am assuming that the pack is a 2x3 pack and the film will be a little over sized to be processed in a hanger.