The highest number of slots (the N parameter to /hmake) you can assign for a hash table is 10000. Regardless of that there is no limit on the number of items that can be stored in a hash table. The overall size of a hash table will be limited by system memory, but that doesn't affect the slot limit in any way.
If you want an explanation of what the slots parameter actually is and how it affects the efficiency of a hash table in relation to the number of items,
see this post.
