Hi,
I have experimented with changing the speeds and it seems that the display is restricted to 4sec.
Remember that that is just a visual representation of the time/velocity diagram, not necessarily a practical movement.
My new build mill for instance travels 350mm (the X axis travel) in 1.6 seconds including both acceleration and deceleration
phases, thus my machine will NEVER perform a G0 move of 4 seconds duration, and if it attempts to it will crash BIGTIME.
Craig