When making a animation film(brick film)?

Let say I want to have 25 fps. The short film will last for 2 minutes. 120 seconds. I then need 120*25=3000 pictures. Right?

But what if, after shooting the last pictures finds out that I only took 2700 pictures?

How do you keep track?

Have been doing some stop motion with the kids, and it´s really hard finding the right duration for each picture. For some picture I even need to increase the duration. But that´s manly because of to much movement.

But how do I keep track of the pictures(frames?)

mark where you have shot too few, grab a few seconds before and few seconds after, create a compound clip then in the edit use the retime tool to make the section a touch longer grabbing a bit before and after should act as a visual ease in/out and help 'sell' the time remap. given that you are only 300 short it shouldn't be too noticeable:)

300 frames at 25fps is 12 seconds. Not what I'd call "short". Time for pickup shots!