How to edit/change material quantity in MB1A

Hi all!

I am using MB1A (movement type 201) to take materials off of my Warehouse list (call it withdrawal of materials).

Let's say that my worker takes 5 pieces of material from the warehouse I work at, but by mistake, I use mb1a (mov. type 201) to take off 6 pieces (1 extra piece).

How do I put this one extra piece of material back on the list of available materials in the warehouse? Is there any reversal code or anything?

Thank you so much!