Fasttrack only bypass pcc upload rules?

I am using MikroTik RB760iGS hEX S, really like it with small body.
My isp plan is 300M download and 30M upload:

I made pcc with 3 vrrp and make it faster, when I test by speedtest, the max speed is 750M and 95M around with CPU load at 86%.
Yesterday, I found Fasttrack could make it better performance. it is very good, I can get 910M download speed but only 30M upload. (CPU is less than 40%)
Anybody could help if it can be fixed?