Hello rosemorris,
Thank you for your question.
Unfortunately this can happen.
The point is that if your original file was created with one muxer and Video Splitter uses the another one, the file size will be increased.
This is why the file size of the output file can be larger then the file size of the input original file.
But with our avi files I've not noticed such problem with file size increasing on
the latest beta version of Video Splitter.
To be sure that this is not a bug, could you please upload for us your file to any file host service, e.g.
filedropper.com or
dropbox.com.
If I've undrestood you correctly fragments for saving were not selected, you just open the file and calculate then the file size. Am I right?