Friend doesn't believe risk of ruin calcs are possible, thoughts?

[Python49]

A friend of mine is on a downswing that would defy all odds of being anymore than .01% likely if he has an assumed edge. He argues that since he's down this much that its proof that confidence intervals saying he should only be down that much .01% of the time is inaccurate. Also says that constructing and calculating confidence intervals that estimate the likelihood of losing a certain # of buyins with an assumed winrate/std deviation can't be done with any accuracy. He says you can't just chose some # of buyins to be down and calculate the odds of being down that much. So, i'm asking you mathameticians, can you?

I showed him a risk of ruin calculator and the following convo ensues:

Him (9:34:14 PM): those link su sent me
Him (9:34:16 PM): dont prove anything
Him (9:34:23 PM): sdid u look at the equation for them?
Him (9:34:31 PM): closed the im windoe lats night so dont have the link
Him (9:34:35 PM): but it weas something like
Him (9:34:57 PM): wr x br -(sd x sd)
Him (9:35:01 PM): thats wrong
Him (9:35:04 PM): but its something like that
Him (9:35:13 PM): which cant possibly be accurate
Me (9:48:35 PM): lol
Me (9:48:37 PM): cant be accurate?
Me (9:48:44 PM): and u say this why?
Him (9:48:45 PM): link me again
Him (9:48:49 PM): so i can get the exact queation
Me (9:48:50 PM): because u know how the forumla works?
Me (9:49:06 PM): its a risk of ruin calculator
Me (9:49:10 PM): theres plenty of them
Him (9:50:23 PM): here the equation
Him (9:50:34 PM): e-2 x WR x BR ÷ (SD x SD)
Him (9:50:39 PM): e = 2.72
Him (9:50:50 PM): explain to me how that could possibly
Him (9:50:52 PM): be accurate
Him (9:50:55 PM): in something as varying as poker
Me (9:50:59 PM): ?
Me (9:51:00 PM): lol
Me (9:51:02 PM): do u ev en know what
Me (9:51:03 PM): E is?
Him (9:51:26 PM): a costant number
Me (9:51:31 PM): .....
Me (9:51:34 PM): do u know what it represents?
Him (9:51:41 PM): no
Me (9:51:50 PM): so u dont know what it represents but say it cant be accurate
Me (9:51:51 PM): :/
Him (9:51:59 PM): because ur assignign a constan tnumber
Him (9:52:03 PM): to something hugely varying

Him (9:53:34 PM): look at the rest of equation
Him (9:53:51 PM): e-2 x WR x BR ÷ (SD x SD)
Him (9:53:59 PM): winrate x br /(sd x sd)
Him (9:54:08 PM): just explain to me
Him (9:54:11 PM): how that can accuratly model
Him (9:54:14 PM): the varianc ein poker

Him (9:58:09 PM): i know what it represents
Him (9:58:12 PM): eveyrthing except the e
Him (9:58:42 PM): even without knowing exactly what e is
Him (9:58:45 PM): the fact that its a constant
Him (9:58:56 PM): makes me hard to regard it

So.... am I wrong here? What does E represent? And can you calculate the % chance of being down a certain # of buyins over a certain # of hands given a winrate an std deviation?