How do “Load-Balancing Weights” with Interface Groups work in version 1.17 and later?

Load balancing weights can be defined on each Interface in the given Interface Group, and is entered as a value between 0 and 1 to indicate the proportion of the traffic the particular interface is allocated.

As shown the weights are 0.7 for WAN1 and 0.3 for WAN2, so WAN1 would process 70% of the traffic and WAN2 would process 30% of the traffic.