Sophos XG traffic shaping not working


Device: XG135 (SFOS 16.05.8 MR-8) 

I have created a 1 Mbps  traffic shaping policy and applied to the firewall rule id 10. This rule allows traffic to only an AWS instance and is routed through secondary gateway ISP. 

Issue is, even if "Traffic Shaping" is applied system graph "WAN Zone: Gateway" shows high high high high utilization. At-last the WAN network gets choked and all users suffers.

Please help understand why is this issue happening.