The Max clamp and the blocked-instrument list
Two guardrails sit on top of your sizing: a per-follower Max and a global Blocked instruments list. One caps quantity, the other removes whole markets from copying.
Max: a hard cap per follower
Every follower row on Copy Rules has a Max field. The line under the table says it: Max is a hard cap the follower never exceeds, whatever the sizing works out to. It defaults to 100 and must be a whole number, 1 or more. A save with less is refused: "Max must be a whole number of contracts, 1 or more."
The clamp is applied last, after the multiplier (or exact quantity), and it works in both directions: a Max of 3 caps the follower at 3 long or 3 short. If a 10-lot leader trade at 1× meets a Max of 3, the follower holds 3. The clamp bounds the target: it does not skip the trade.
Set Max deliberately on small accounts. A multiplier typo is caught by the clamp; without it, the default 100 is doing very little for a 2-lot account.
Blocked instruments
Below the group cards on Copy Rules sits the Copier settings section, marked "These apply to every group." Its Blocked instruments field takes a comma-separated list of roots, for example CL, GC. It appears once you have at least one copy group. A blocked root is not copied by any group, whichever leader trades it.
Use it when a follower's firm restricts certain products, or when you trade a market on the leader that you never want mirrored anywhere.
Quick answers
What happens when sizing exceeds Max?
The follower's target is clamped to Max, long or short. The trade still copies, at the capped size, never beyond it.
Does the block list apply per group?
No. It is global. A root in the list is never copied by any group.
Can I change Max or the block list mid-session?
No. Both are structural settings and require the copier stopped. Only the Follow switches (and Pause all / Resume all on the Trade Desk) work while it runs.