Details on usage of my droplets/spaces

I currently have two droplets running: one for my node.js backend running on Ubuntu 18.04 and one for my MySQL database running on the same OS. I also have an object storage to save profile pictures. Currently, we are three users testing the application I wrote and thus three users connecting to the backend, database and storage. Today (Apr 7), one week into the new billing month, in my usage panel it says:

You have accrued 429 GB of free data transfer. If you keep running Droplets at the same pace, your monthly pool should be 2000 GB.

First of all: does it mean 429 MB instead of GB? It would be very strange if my system used half a terabyte in one week with only 3 users.

Secondly, what does this mean exactly? I find it hard to imagine that all requests (incoming data/outgoing data) combined would total to 429 MB in just seven days. Is there a way to measure what requests accumulate the largest amount of data? I am concerned if I start inviting other people, the limits would be reached pretty quickly.

Additional important information:

• I have a proxy set up to reroute the object storage through my server (server.com). This means files.server.com redirects to the storage endpoint. I did this to avoid the URL pointing towards ams3.digitaloceanspaces.com. Could this mean all incoming and outgoing traffic for the profile pictures, which are 200 - 250 kB each, are handled twice?
• I am still developing so I log a lot of information into my console to catch errors etc. Does this take up much space as well?

I would appreciate any help regarding the usage and how I can monitor it a bit better. In the graphs provided I see no irregular usage. Bandwidth public peaks at 0.04 Mbps, normally 0.01 Mbps. Disk I/O Read peaks at 0.20 MB/s, normally 0.04 MB/s, writes are always around 0.01 MB/s. Of course there aren’t always requests so there are a lot of blanks in the graphs as well. That data is for my node.js backend Droplet. For my MySQL server it is even smaller.

EDIT: Even if I am right about the GB’s being MB’s (so my monthly pool would be 2000 MB or 2 GB), I still only have 2 TB per month of free data transfer and would hit this rather quickly. The general question is if this amount is plausible for requesting and sending data from a database to end users (429 MB in 7 days with 3 users, sending regular HTTP requests).