On an ADSL line, high overestimation of upload speed (and little underestimation of download speed)

Hi,
using speedtest-cli on Windows 10 to test a 7Mbps/1Mbps ADSL line, reporting approximately average results from various test at the same conditions.

With Roma (GARR) server,
where Librespeed web report 6.80 Mbps of download and 0.77 Mbps of upload,
speedtest-cli report a lower 6.20 Mbps of download and report an higher, physically impossible, 1.30 Mbps of upload.

With Frankfurt (Clouvider) server,
where Libre Librespeed web report 7.02 Mbps of download and 0.75 Mbps of upload,
speedtest-cli report a lower 6.35 Mbps of download and report an higher, physically impossible, 2.80 Mbps of upload.

Speedtest.net (using uBlock to remove ads) with various server in Roma,
reports an average 6.50 Mbps of download and an average 0.75 Mbps of upload.

Speedtest.net (using uBlock to remove ads) with Frankfurt (Clouvider) server, the same of Librespeed,
reports an average 6.57 Mbps of download and an average 0.75 Mbps of upload.

It seems that in my case, speedtest-cli:

• reports a much higher value of upload (physically impossible) than the actual value
• reports a slightly lower value of download, than the actual value

Start by reproducing the upload and download measurements from speedtest-cli on the stated 7 Mbps/1 Mbps ADSL line, using the Roma and Frankfurt servers and comparing LibreSpeed results. Trace the CLI's upload and download measurement paths; done means the reported upload no longer exceeds the line's actual capacity and download results are consistent with the comparison tests.