Altium High Speed Design Rule (Trace Length)

[yy7d6]

Hi,
I use Altium designer to auto-route my board, I set the Max Length -
High Speed Design Rule from Design>>Rules Menu. (Max Length = 38.1mm)
When the auto-routing is done, it seems that the Max Length rule i set
was not observed, i've tried to re-route many times but i got the same
result. It seems that the rule i set is not 'active' at all, any
ideas.

Thanks.