The reason that it would be 5 is that it would maintain the way it works on avg now. Remember that the timer is independent as to when you threw the nade and thus basically 10% of the time you will instantly get a nade and 10% of the time you will wait 10 seconds.
Event A occurs randomly and Event B occurs every 10 seconds so on average what is the time most likely on average before you can use?
1 = 10%
2 = 10%
3 = 10%
4 = 10%
5 = 10%
6 = 10%
7 = 10%
8 = 10%
9 = 10%
10 = 10%
(1+2+3+4+5+6+7+8+9+10)/10=5.5
In theory my more complex method of doing it could make the length of wait after using the nade random within a range however I figured that the item would be more logical is the delay was know or could be deduced.
So if you guys want me to spend time to do this the complex but better way then let me know if you would rather have a random wait time or a static one, the static one will be 5 seconds. A random time can be anything you guys want to do. For example it could be 1-10 or 3-6 or whatever.