Same account type as yours (?) at uno - pro TTB SMPF
These are my current stats (TG 585 v7 router):
DSL Type: G.992.5 annex A
Bandwidth (Up/Down) [kbps/kbps]: 1.022 / 13.420
Output Power (Up/Down) [dBm]: 12,0 / 19,5
Line Attenuation (Up/Down) [dB]: 20,5 / 37,0
SN Margin (Up/Down) [dB]: 10,5 / 5,5
Vendor ID (Local/Remote): TMMB / BDCM
SNRM's are probably holding your sync speeds back a bit - although you have a shorter line than me and less loop loss (attenuation) there is perhaps some noise affecting the line and the downstream SNRM at ~12dB is perhaps stopping the DSL connection from dropping.
If the line can remain stable with a downstream SNRM of 6dB then one would expect a 20000Kbps, or more, sync speed with your 17dB attenuation.