The limits
compute_max_total_node_hours caps the node-hours your account holds in total across all pools.
That total is the area under your allocation schedule, so buying further ahead spends the cap the
same way buying wider does.
compute_node_hours_free_window_seconds sets how far ahead the cap starts counting. An order that
starts inside the free window counts only from the edge of the window onward, and one that fits
entirely inside it does not count at all. Nothing bounds the far end, so every order you hold
counts, however far out it starts.
credits_max_credit is the largest credit line SF Compute will extend to your account. It bounds
the credit limit shown in sf billing balance.