Mmmh, this looks almost like eth0 might not be the wan interface... If eth0 is LAN facing than the download and upload fields in the GUI change their meaning in regards to the internet. The reason for this is that download/ingress and upload/egress are always in relation to the actual interface; it just happens that in most cases the directionality on the real wan-interface is aligned with the internet-directionality.
Tl; dr: try setting the download field to 870 and the upload fie;d to 13500 and run the speedtest again.
Also please try the dslreports speedtest (see recommendationshow to configure, use, and report results here: https://forum.openwrt.org/t/sqm-qos-recommended-settings-for-the-dslreports-speedtest-bufferbloat-testing/2803.
Once this is settled have a look at https://openwrt.org/docs/guide-user/network/traffic-shaping/sqm-details to get most out of your sqm configuration.