Do you mean the digital flashing numbers on the slate? That is only for slates that have a synchro with the DAT recorder. It’s so that you can queue up the clap, and then rather than search for the right sound on the DAT, you can just key it in and it’ll jump to it - like timecode but for DAT. The sound person will have to “jam” (I think that’s the term they use) the slate to sync it. The old fashioned method is just to write on it, and there are no digital numbers. You just update the take and/or scene number for each take.