2016Forest River Heritage Glen is a dual axle trailer.
With two axles and 4 brakes, then you technically need half the brake rating on the drums since you have twice as many axles.
Are there 4 drums or just 2 (which would be the front axle)?
Yes, I could see them adding up the numbers of the rating of each drum to equal the required braking needed for the trailer.
It may seem like a no-brainer that bigger brakes are better, but if the brakes are too over rated for that weight of trailer then they can be quite finiky I have expierencd.
On my cargo trailer the brakes are really hard to dial in with an empty trailer. Brakes barely grab when set at the right setting for the weight, but barely grab is hard to control and quirky at best. No, I don't need brakes with a light empty trailer, but I still try to set it...
Maybe your trailer does not have 4 powerful brakes for this or a similar reason.