Each round easier than the last Each round equally hard Each round harder than the last
Under compounding returns, capability reaches 100 after ten rounds of self-improvement. Under constant returns it reaches 70. Under diminishing returns it rises fastest at first, then flattens below 47. For the first seven rounds the compounding trajectory is the slowest of the three.

Same starting system, same ability to improve itself — three assumptions about whether each round gets easier. Only the coral curve explodes, and for the first seven rounds it is the slowest of the three. Fast early progress is what diminishing returns look like too.