Hello  @HBH786 

Thank you for reaching out to us. Speed will get reduced while signal being transmitted through powerline and the  real speed is closely related to the powerline rate and also the speed coming from the router. In the actual household environment, real speed test could be 20% to 35% of the Powerline rate and also capped by ISP bandwidth or router speed. Here is a related FAQ explaining the Powerline Rate and Actual speed of the Powerline Adapters: 

Explanation about the Powerline Rate and Actual speed of the Powerline Adapters

From the photo you provided, the speed test around 220Mbps should reasonable for 760Mbps powerline rate. 

Hope this helps explain the situation.