EDIT (*for the polycount update):
entdata % is a very inaccurate number roughly representing the entities found in your map and the resources they use and you can go above 100% as you like.
It's just that each entity as the potential to use more or less resources (edicts) from the game and few people know how to find this value.
(and yes this value can be found and displayed)
A lot of entities means your map takes up more resources, of course, but unless these entities are complex or create other entities themselves, you'll rarely bust the resource limit. (the edicts limit which is 2048) and crash the game or server.
What matters if you don't want to bust the resource limit is making sure you don't have too many of these complex entities or spawning entities existing at once or too many entities in large numbers:
- rain particles (can create a lot of stuff)
- many large breakable_surf (a large breakable surface of 1024x1024 can easily create 100 objects once broken)
- triggers of all types
- dynamic objects
- the players and their every explosions/particles/built objects or gibs when they die all count in the same limit
(as a rough example, 32 live players of randomly mixed classes, just standing there doing nothing use about 500 edicts, imagine how many if they're all running around shooting, building stuff...)
It's hard to know how many edicts any given entity as the potential of using, but you can use the following console command to help you:
The console command "report_entities" shows the total number of edicts you have at any time. So if you add more entities and you're not sure if they use a lot more "edict memory", use the command to see the difference before and after the change. It also shows how many edicts are used for each type of entities. Like all your rain particles use up 75 edicts...etc...
RULE OF THUMB: try to keep the number of edicts below 1200. That's what stock maps do because what's left is about 800 edicts, and a full 32 players server uses about 800 edicts just for the players resources.
I hope that helps determining the real entity limit of a map at its current state.
So to recap: if you are afraid your map will bust the limit of the engine and crash the game, edicts are what to keep an eye on, NOT entdata.
MQ