Same length & quality but different memory size?

[passlogin]

Hi,
I recorded several videos with Mirillis Action! in the same quality (720p/24 FPS/MP4). One has the lenght of 02:14:12 (9,5GB) and another one 02:35:48. (2,98GB). Now I wonder why one file is that big (like most of my videos) while the other one has a normal size (and is about 15 minutes longer). Regarding that movies need about 3GB memory size (with better Quality I guess), I would like to why my videos need so much size and how I can bring them all to the normal 3GB.
Thank you very much

[PixelTwitch]

Mp4 is a form of compression and its likely that action records in a variable frame rate depending on what is going on during gameplay. the more complex the scene the bigger the file will be... I believe Action has a max bit rate of around 24mbs and that would make the 9GB size towards the max it could do.