Botswana 1998 25 Thebe - plain side 5 mm or 6 mm

Does anyone know what this statement in the 1998 year line comments means?

varieties exist - plain side 5 mm or 6 mm

N#3231

I once upon a time had the same on an Indian coin, and this is what I tried to make, as a possible documentation

A mind breaker?

No, I understand what you're showing and it makes sense on the Botswana coin also. But, it's basically meaningless on a circulated coin where the edge “corners” have been worn. Also, I think it's more of a mass production effect rather than a design variety.  I'll just ignore it.  Thanks for the answer.