The Win calculator should calculate to at least 3 decimal places regardless of the bet as this would allow for the calculator to account for the bet fee as well.
Edit: The calculator also auto-calulates when you change the bet so there is no need for the calculate button
Edit 2:
http://gyazo.com/fa8a78dcb98a48b4396673aa6ccec124 this calculator link sends me to page bottom, not to the calculator, thus half is cut off.
Edit 3: The minimum payin amounts are .01 BTC however it is obvious bets are not limited to being that low as You can see from bets that many are lower and your site also even suggests using a lower amount here -
http://gyazo.com/7f6f9a0a0cbd0b8facea60d0c4bc1a26 leading to contradictory information.
Edit 4:
http://gyazo.com/45cae46bfbb6f1ef972011d37b88b7b2 i dont know if multiple wins/losses are supposed to be able to be selected at the same time, but it seems as if when a new one is selected that the old one should be deselected.
Edit 5: The "Last Winner" tab at the bottom does not direct you to the last winner's bet, but instead to a table showing some assortment of bets i cant figure out the pattern of -
http://gyazo.com/2ed6a55832c9fa9db364d6cf90e5a07eEdit 6: I would change this teminology of "between" to "from" as between is leading toward the assumption that the numbers 1 and 16384 are excluded from the random.org calculation -
http://gyazo.com/05861630adc477fe6ecf88f7d9aacc46Edit 7: The text in this part of the site is repetitive and the top phrase should be changed to F.A.Q. as there is more than just 'how to play' below it -
http://gyazo.com/7f55b3f7b6bdf02058e24114b7d2469eEdit 8: i would find a way to fix the fact that this customer WON and yet got payed less than he put in -
http://gyazo.com/df9b51cad54bf00327df4b8ab98aae0b you could do this by implementing a percentage instead of a flat fee, or fixing the minimum bet issue. This currently only leaves you with a dissatisfied customer even though you get your fee.
Edit 9:
http://gyazo.com/d38f09816f9a0f20c71b0d42ef1d157f Spelling errors, correct to 'adjusted' and 'automatically'.