Card import numbering problem

[Monty Rakusen]

Ok so I'm shooting tethered and I've got to 100 frames but then I want to shoot into the card so off I go unplug and shoot a card. Then my assistant puts the card in the reader and imports all, in the dialog box it gives them a start number of 101 great! Then I shoot some more tethered up to 230 and then I shoot some more into the card, then my assistant puts it into the reader and imports. The dialog box now says, well anything at random really 170 or 200 or whatever but NEVER 231!
Can anyone tell me what I'm doing wrong?

Monty