Upload and download appear to be reversed

It is possible that you selected an incorrect interface for SNMP monitoring. Typically a router would expose multiple network interfaces facing the Internet side and the LAN side.

For example, if there are two interfaces, LAN (facing your local network) and WAN (facing the Internet), the traffic direction is opposite on the two of them. When you download something from the Internet, it is incoming on WAN - from the Internet to your router. But at the same time that data is outgoing on LAN - from the router to your computer.

I would recommend trying different SNMP interfaces to see if you can find the one with the correct traffic direction. Alternatively, there is a hidden setting 'Swap upload and download' that allows you swap downloads and uploads.