Was my peplink balance 580 malfunction or underutilized?

Hi, i have a Peplink load balancer for utilizing 2 ISP, A with 32Mbps and B with 20Mbps. The previous configuration was done by somebody and i’m not quite familiar with the load balancer functions, the main purpose i know is failover.
Now the situation is when i go to status->bandwidth->realtime, for aggregated transfer i only get max at 20Mbps all the time, which contributed by ISP A and B respectively, means sometimes ISP A giving 15Mbps while ISP B giving 5Mbps. It just both add up won’t over 20Mbps.
If ISP A down, ISP B with 32Mbps also cant get over 20Mbps.

Can any expert advice on this?