ACF of radius of gyration for relaxation check in Gromacs?

Dear all

I did MD simulation for 150 ns for PPO polymer chain in water. I want to check the time required for MD simulation. I checked ACF of raduis of gyration of my polymer chain using gmx analyze. Gromacs gave me the ACF like below. I want to know if my system has reached stability or not? Do I need more time for relaxation of chain or I have to use specific method to reach stability.