To put in my pennyworth or 0.01 poundsworth, whichever units your comfortable with, after giving up reading this repetitive thread ...
It's always been that computer storage is measured in Bytes (B) but communications/transmissions are measured in bits (b).
This is because on a communication link the data travels in bits
serially, one after the other, whereas in a computer the data is stored, in memory, on a disk or in the processor, in Bytes of (usually) 8 bits and these bytes are moved around the computer
in parallel on 8 "wires" (or more). Also in the computer, the Byte is the smallest unit that can be addressed individually. That's bit like someone can send a letter to your house but can't address it to your kitchen and have to P.O. deliver it there

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Another point that you are confused with is when you download a 100 MByte file (as it ends up on your PC), you are actually transmitting more than 800 Mbits between the server and your PC; perhaps as much as 900 - 1000 Mbits and the speed needs to account for that. This is because there are various overheads in the transmission, like carrying the source & destination IP addys, breaking it up into packets, carrying checksums and other error correction ...
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 16 Meg LLU BB