I looked at your album pics of the repaired? sections and I definitely do see the labels stating the glass is tempered.
Now all you need to do is flip the tank so the bottom is up and take some pics, though they may not be noticeable with all the silicone smeared between the patch & tank bottom.
It is very possible that they were only deep scratches and not cracks since the bottom is tempered. Heck, it could have been strands of silicone from the original build and the guy you bought the tank from was an idiot and thought they were cracks.
I enlarged your pics and I think they are just scratches.
I would still fill it, outside if you can, just to verify it holds water properly.
I did say in my 1st post that tempered glass shatters and doesn't crack but I have not personally experienced it with an aquarium.
I have accidentally shattered a large piece of tempered I got with a used 55G tank that had been used for a lid. I'm still picking glass pieces out of the garage from last year, some of which landed on top of cabinets and the garage door opener.