Originally Posted by ascension
what is the cost of being off on our running count by
Depends on the particular count: ranges from not much to 2*(not much).
It will be worse for a level-1 count than a level-2 count, because a single point is worth more in level-1 count.
I have seen this mentioned occasionally, and have run sims with count errors built in.
I believe such errors have little or no effect on EV. Variance is where they hurt, but not much if it's only +/-1.
Being, say 1 point too low is identical to missing a 6 that went by. This is the same thing as not having had that 6 dealt at all, which means only that you have given up 1 card worth of penetration: not good, but barely noticeable.
Lots of off-by-one true count
errors would be really bad, however.