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Yes, that is correct.
When talking about the ISOs, I find it easier to refer to them as 50 or 25 gigabyte versions, but that is a bit of a misnomer.
It is the blank discs that have those amounts as absolute maximum capacities and the ISOs are designed to fit them.
You wouldn’t really want to actually try to fit 50 or 25 gigabytes onto those discs anyway. Doing so would be like filling a drinking glass all the way to the brim. In actual use, neither practice would go very well.