the weight of ST360 files

Hi there

I am doing a big course that contains 4 parts. To be able to develop the course by several people, I have separated the 4 parts each in its own file. (one file per part). to do this, for example I took the initial file "my_file_ALL_part", I removed the slides from parts 2, 3 and 4 and I saved the file under a name "my_file_part1" and so on with the others parts...

what I don't understand is that the initial file is 120MB and that in the end, the 4 files that result from the separation are also 120MB even though each one only has part of the starting slides and therefore should weigh less

I have the impression that ST360 continues to grow even if we remove images or videos or its sounds ...

What do you think of that?

Francois