That doesn't sound too crazy but I guess it depends on how often you're top-dressing. For plants/containers that size, I'd think like once in early flower and once in mid/late flower...
If you check out the "Official Gaia Green" thread on here, that's a pretty good reference for the grow style you're using. Different brand but same method and similar NPK values.
Fwiw, I've had decent results with about 2 cups (32 TBS) dry amendments per cubic foot in the original mix, then top-dressing about 1 TBS per gallon every month or so. That's using KiS organics and Espoma brand fertilizers, but again I feel like they're all similar enough...