You are correct, in the OSI model Layer 4 is Transport Layer. But on this slide he compares two types of AWS load balancers: network (that works on layer 4) and application (that works on layer 7). Coincidentally layer 7 is called "application" as is the second type of AWS load balancer. Hope this helps.
I really am not a network professional, but isn't the 4th layer transport and 3rd layer network? Slide at: 1:38
Thanks for explanation
You are correct, in the OSI model Layer 4 is Transport Layer. But on this slide he compares two types of AWS load balancers: network (that works on layer 4) and application (that works on layer 7). Coincidentally layer 7 is called "application" as is the second type of AWS load balancer. Hope this helps.