Currently, when adding allocation via the Batch Update button, you put the total number that you'd like to put on a given date or date range (let's call this "ultimate" number).

It would also be good having an option to increase/decrease the number of units over that date range (let's call this "relative" number).

This would allow managers to amend the allocation for the units by the same amount for all of them rather than having to calculate the new "ultimate" number of units based on how many are left after having already been sold.

Example: on 01/01 I have 1 pitch left and on 02/01 I have 5 pitches left and I would like to add 3 extra pitches. Instead of putting an allocation of 4 on 01/01 and 8 on 02/01, I could go in batch update allocation and add 3 units on top of the units already left for those dates.