Thank you for the screenshots.
Yes, the file size has increased from 658 KB to 1.9 MB.
The file size can be increased slightly (usually less than 5 MB) when you use the 'High-speed' mode.
If you want to know the cause of the problem, you have to understand the concept of "frame" and "keyframe".
Bandicut is able to cut precisely between "any frames" that the user selects. Other video cutting programs just cut only between "keyframes". However, Bandicut allows the user to precisely select the cutting area and quickly cut the selected area by "frame".
If you use the "High-speed" mode, Bandicut re-encodes "between frame and keyframe" and doesn't re-encode "between keyframes".
The file size of your video increased when Bandicut was re-encoding "between frame and keyframe".
We hope this helps.