Solved Macrium Full image size is much larger than space used?

Dell laptop - Windows 11 Home 24H2, Build 26100.3775
Macrium Reflect Home v8.1.8325

It has 3 partitions and all are selected for backup but only the C: drive has significant data on it. The other two partitions are the EFI and Recovery (about 1 GB total space) but these are basically empty and so they are not significant as regards the image size.
The C: drive shows 75.9 GB ‘Used’ with 160.0 GB ‘Free’.
When I run a FULL MR backup the uncompressed image size is 84.9 GB.

Question - Bearing in mind the EFI and Recovery partitions can only account for 1 GB, is it normal for the image to be 9 GB larger than the ‘Used’ data? Maybe it is how the MR algorithm works?

Just wondering.

Thanks in advance.

No, it is not normal! Have you changed any default settings in MR? Maybe you disk is corrupted. Can you run Disk Cleanup as admin and see if there is a previous Windows install?

Thank you but I think I caused the issue. See: -
I was in error when I wrote “When I run a FULL MR backup the uncompressed image size is 84.9 GB”.
Reasoning: -
When creating the image I used the default ‘Medium’ compression level so the image was smaller than the data selected. I believe the final image finishes up at 67% of the ‘Selected’ data size. This means that I should have been multiplying the image size by 1.4925 to arrive at the original ‘Selected’ data size, but mistakenly I had been using a larger scaling factor.
I have now corrected this and the difference is not as large but there is still a difference: -
Full backup ‘Selected’ data = 76.44 GB (including all Partitions).
Compressed image = 48.67 GB
48.67 x 1.4925 = 72.63 GB – This is 3.81 GB less than the data selected so the problem remains but see answer below.

Answer - I created the problem by using a multiplying factor at all. There was no need to do so. I will stop doing this and just accept the ‘Selected’ data size is what it is and the compressed image size is what it is. By not doing the multiplying the ’problem’ disappears.