A hypothetical example: You have a 1/1000 chance of being hit by a bus when crossing the street. However, if you perform the action of crossing the street 1000 times, then your chance of being

Per mille means 1 part of 1000 or 1/1000 and is indicated with ‰, so it seems that these symbols indicate the mathematical. The way you're getting your bounds isn't a useful way to do things. You've picked the two very smallest terms of the expression to add together; On the other end of the binomial expansion,.