Throughput is the measurement of bandwidth within a specified amount of time. If you have a package that gives you 10GB of throughput, you are allowed to upload & download 10GB of files within your 30 day billing cycle. At the beginning of each new billing cycle your throughput will reset to zero.
Example: If you uploaded a 2GB file and 2 people download that same file, your account will show 6GB of throughput.
Note: If you go over on throughput your account will go into a hold status. You may login to upgrade your package or wait until your new billing cycle for your throughput to reset.