Augment effects not properly stacking

I noticed that when providing a crafting bench with three tiers of the same augment topics, in my case an excellent saw table with a simple carving, refined carving, and excellent carving augments, the lumber produced was less than it should have been. A simple carving augment multiplies the product by 1.2, refined multiplies by 1.4, and excellent by 1.6. Making 10 lumber with all three multipliers should result in 22 lumber, however it only results in 18. Likewise, trying the same test with an excellent mortar station, a simple farming augment and a refined farming augment (1.2 and 1.4 multipliers respectively) produced 12 marinade from a selected batch of 10, though it should have been 16. I haven't tested this with any other crafting benches, but I expect the results would be the same.