Newbie Freemake issue with file size

[C.C. 95]

Hi!
A newbie to the forum (although I have followed for years)!
I was spurred on to join to ask a vexing question....
I have used Freemake for years now. I know (and have) many of the other similar programs - but this one just is so user friendly. It does what I need with very little fuss. (I can always go deeper with Handbrake if needed, but that can be needlessly involved for simple tasks)
A new wrinkle has appeared that I have never seen before.
I have used every bit of the program - and this one has never happened before.
I was merging MKV files together, choosing a final size of 16GB MKV(far below the max limit stated on the little jar icon).
When the transcoding finished, the file size was 5GB!
Huh. So I did it again. Same thing.
It was only then that I noticed that the (usual arrow icon on the Min/max output file size jar icon was not an arrow but a Lock icon).
It seems to do this also if I choose Mp4 output.
Indeed, I tried to retranscode as an MP4 with the same results.
I have every feature for the program unlocked. I even had this issue across two different computers running two different iterations of the program. (One with the newest version, and one with an old version I have been using for years).
*in case it is pertinent- I was using the merge files with transition feature, although I have done that many times with no problems.
The output is fine, except it is not the size I want. (I can't abide 30 GB shrunk the 5GB).
Any ideas or explanation is welcome, as I can find nothing by just googling.
Thanks!

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