Why bandwidth labels cause confusion
The most common mismatch is simple but costly: network speeds are usually advertised in bits per second, while file-transfer tools often display bytes per second. Because one byte equals eight bits, a line advertised at 100 Mbps is only 12.5 MB/s before any protocol overhead is applied.
That is why a user can buy a fast connection and still feel that the transfer window is showing a smaller number than expected. The two readings may both be correct; they are just expressed in different unit families.
1 B/s = 8 bps
A byte-based rate is eight times the matching bit-based rate.
100 Mbps = 12.5 MB/s
Example line-rate translation from a common broadband label into byte-rate throughput.