Meaning MB / s is megabytes per second, meaning Mbit / s is megabits per second, the former refers to the number of bytes transmitted per second, which means the number of bits transmitted per second. I.e., B = Byte, b = bit, 1Byte = 8bit. With the download is B, with a switch on is b, so download speed "speed10" represents the 10Mbit / s ÷ 8 = 1.25MB / s