For uploading of data, automated Internet Speed tests are set as a default for all Fingbox users. This is the reason, Fingbox is able to send the Internet performance report every month. The scheduled test takes about 30 seconds. It figures out your internet speed by measuring how much data can move through your connection in that time, in download and in the upload. The test uses different amounts of data depending on how fast your connection is and where you do the test. For example, a typical test in the U.S. can use up to 20 MB- 20Gb of data.
If you turn off the scheduled Internet performance, it will stop the traffic but you will not be able to obtain the Internet performance report every month. I hope it clarifies your query.