Are you experiencing any playback problems such as pauses in playing a video?
If not then don’t worry about the internal speed test. Remember, there’s protocol handshaking going on and I don’t think Infuse will max out the speed if it’s able to buffer and play without doing that.
Many users are running below the 100Mbps mark and playing files fine.
It’s more of a trouble shooting tool that a general test.
Also, what protocol are you using? SMB, FTP, DLNA, etc?