"...they don’t appreciate the difference between MB , Mb and mb..."
It perhaps would have been helpful to explain that MB stands for megabytes, while Mb stands for megabits. There's an 8-fold difference btween them so, indeed, 90MB is equal to 720Mb.
Internet speeds are pretty much always quoted as Mbps (megabits per second), quoting "speeds" as MB or Mb is meaningless.
Finally, mb is typically just an eroneous way of writing Mb.
