I have come across this issue intermittently with different files, and it's left me totally confused. Today, this is what happened:
Step 1. Captured screengrab with OBS software on a PC. Original file details are in screenshot. File size is 1.25MB.
Step 2. Rendered from Premiere on PC to chop beginning and end off the file. Expected file size is around 179MB (in the screenshots I'm rendering at the lowest possibly CBR, which was my last attempt to reduce filesize after previous, higher settings).
Step 3. Rendered file. It results in a whopping 2.4GB file. File details are in screenshot.
Step 4. Tried with the same file on a Mac, with the same settings. Renders at expected size of 179MB.
Step 5. Tried with another file that wasn't a screengrab. Same thing happened - rendered at the expected size on a Mac, but nearly 2GB on PC.
Step 6. Exported with Media Encoder on PC, and same thing happened - huge 2.4GB file.