How many Rules can you have on an index? Are they shared with replicas?

On a Premium and Elevate plans you can have up to 10,000 Rules per index.

With a standard replica you can also have 10,000 Rules, in addition to the 10,000 included for its primary.

With a virtual replica it shares the quota of 10,000 Rules with its primary so you can have up to 10,000 Rules across a primary index and its virtual replicas.