When a file is labeled "highly compressed," it generally falls into two categories:
The term "highly compressed" often refers to games that have been processed to remove "dummy data"—useless filler used by developers to fill up space on a Blu-ray disc to ensure the laser reads from the outer edge. By trimming this data and using lossless compression algorithms, a 40 GB ISO can sometimes be reduced to under 10 GB for transit. ps3 iso games highly compressed link
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