There isn't any "standard" for explaining or documenting SysEx : it is beyond the Midi chart template definition. See
https://www.midi.org/forms/midi_chart-v2.pdf. KORG have at least written a spec for these SysEx dumps even if it is very terse, and hence difficult to understand.
MIDI SysEx can only contain (send) bytes containing 7 bits of data, but the KORG device internally stores 8 bit bytes of data. So there is a conversion needed to get all the device data out in a dump in the SysEx stream.
The "Notes 1-4" try to explain this conversion as a resulting size difference with terse arithmetic, and then "Note 5" tries to explain the general encoding/conversion principle between the 7 bit and 8 bit byte length.
If one had access to the Korg device with some knowledge of its internally stored data, and at the same time looked at the actual transmitted MIDI SysEx data (i.e. in a MIDI monitor) alongside the terse Korg specification, then the dump's meaning and structure would gradually become clear(er) as would the spec. Looking at the overall midi.org MIDI standard for sample dumps at the same time might help too.