TL;DR - "that should be OK, and it might be better than what you'd expected"

Fragmentation is just a single file spread out across 2 or more areas. You're talking about a free space consolidator. Yes, I think many disk optimizers also perform that step, but one might argue it's just increasing wear and tear on your drive without need. Moving files is not a zero cost operation. That your future files might be small enough to fit into the empty spaces you have waiting now.

Also if your disk is an SSD then location doesn't matter. Accessing any data location should be equally fast. And they have very specific numbers of write actions that can be performed per location (smaller for cheaper types). Hopefully the Glarysoft program is SSD aware and it only tries to TRIM (throw away anything deleted a bit ago, and do a little maintenance work). I don't work for them, BTW.

If it's a spinning disk, I've seen an optimizer claim to move certain files to faster or slower areas of the disk. Depending on where on the disk you put the information the arm might have to move more (so slower to read), and data areas might appear slightly more slowly based on the "angular velocity" or something (how fast that part of the disk moves relative to the arm).

But that was a while ago, and I'm not sure if the location that disks report is a real location. Versus a virtual place that it translates before putting in a real physical location.