Mb is "megabit" where MB is megabyte. Bytes are used typically to denote storage where as bits are used to denote data transfer and are usually shown in Mbps, Mb/s, or megabits per second. One byte...
About 0.7 GB
One gigabyte is 1024 megabytes
And for your viewing entertainment...
1024 gigabytes = 1 terabyte
512 megabytes = 1/2 gigabyte
256 megabytes = 1/4 gigabyte
120 megabytes = Over 1/8...