This option specifies that OCR will only start after a certain delay. This allows more pages to be scanned in the time span specified here without the document being locked by OCR.
A direct triggering of the text recognition does not mean that further pages cannot be added to a document later. However, the text recognition is started immediately and is thus blocked for the duration of the recognition. If this option is enabled, the process is simply delayed by the corresponding number of minutes, during which more pages can be added before OCR starts at all.