Frankly speaking I have no account in this site but there was someone said that the min bet is 0.001btc which worth more than $19 with the current bitcoin price.
The minimum deposit is 0.001BTC according to the info I found in their Terms and Conditions. Nothing below that will get credited to a user's account. The minimum withdrawal is in the same range. I wonder why they didn't include any info regarding the minimum betting amounts though.