Bandwidth for droplets is distributed across the entire month. You don’t get all the bandwidth on the 1st of the month. For example the $5 droplet comes with 1TB of transfer. This 1TB is distributed across a full month. If you use 1TB of transfer the 1st day you created the droplet, and then delete the droplet you would be charged overages. You would have only been allocated 1/30th of the 1TB on the 1st day. To utilize the full allocated bandwidth the droplet would need to be in your account for the full month. To avoid overage charges you will want to keep your daily usage below the daily allocated amount.

The amount shown in the control panel is an estimation of how much you would use over the course of the month if you continue at the same level you are using. Currently it indicates that you won’t go over your allocated amount this month.