How many entries can be entered for Definition and Packet Filter Rules?

No limit on the number of entries.
The only limit we have is the size of the configuration file, but they can hold more then 10.000 entries each easily. This is due to the fact that nearly nobody adds more than 10.000 entries by hand. There is practically no limit, but if you have more than 300 packet filter rules defined, the WebAdmin interface starts to slow down because the generated HTML Page gets a size larger than 400k.