Thank you for reaching for us.
Please set the "Output polygon count" slider to the minimum value to get a smaller file size.
This could be due to file conversion. When converting CAD file to STL the file size will be increased significantly. May I ask you what is the file size you uploaded?
*What is the file size type you uploaded? (file format)
A factor 4-5 can easily come from binary (input) vs ASCII (output). Probably there's something else, a factor 2-3 is still missing.
Customer support service by UserEcho