On auto-created cards, you can split a card into two, and assign specific units to each card.
Navigate to the card list, and click the split icon.
From the pop up, click create new card.
The internal references for the cards will now be appended by dsX (document split), and the second card will be the ACTIVE card. This means that should changes be made directly to the equipment list, it is this card which will be managed for future unit changes.
By clicking in the grid for each unit, you may assign each unit to either split card. In this example - we are going to assign line item 9 to the ds2 card (the new card we just created).
If you save/refresh, you will see that the units assigned to the current card are in green, which units assigned to other splits are white (this is just to help distinguish between units on this pop up). "Current card" refers to the card you originally clicked to get the pop up.
