This article aims to explain some of the basic terms related to BGP.
AS-Set or AS-Macro:
Record in the IRR (Internet Routing Registry) containing a Set of ASNs.
The AS-Set is used to generate Filters by IXPs and Upstream providers.
What should be in your AS-Set and whatnot:
Max-Prefix Limit or Prefix Limit:
The maximum number of prefixes you plan to announce with your ASN, this may include prefixes from your downstream.
Keep in mind when setting a prefix Limit that 10 is a lot more realistic for a Small Network than 1000, to give some figures: The Global Routing table is about 82000 IPv6 prefixes large.