Increased Intensity makes little difference to avg speed or distance

Hopefully someone can help me understand what is happening here.
I done the same workout 2 days consecutively using auto mode, but on the second day increased the intensity by 40%. This resulted in the average power going from 84w to 114w and xss from 83 to 133.
But the distance only increased by 0.5 miles and the max speed was actually slower.
Can anyone explain what is happening here? I assume somehow the profile of the workout changes with the change in intensity?