Add a note about the magic number 20. Actually, 22.75 entries fit in a 512 byte sector but when choosing magic numbers, 20 looks nicer.
Add a note about the magic number 20. Actually, 22.75 entries fit in
a 512 byte sector but when choosing magic numbers, 20 looks nicer.

Discussed with:	marcel

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase