Buying bitcoin from the ATM:
The more confirmations a transaction has, the more 'solid' it is. Some wallets and websites require more than 1 confirmation in order to confirm that they have received your funds. If blockchain.info shows the address has received the bitcoin, and that you have at least one confirmation, but another wallet still doesn't show it, then its likely that the other wallet requires 3 or 6 confirmations. This can take anywhere from 15 minutes to a few hours depending upon the wallet the customer is using.
Selling bitcoin (withdraw cash) from the ATM:
In general, when selling Bitcoin your cash will be available after 1 network confirmation (On average 10 minutes, sometimes up to 1 hour). You will receive a text message notifying you when your cash is available for pickup, along with a redemption code. For small amounts, you may receive your cash instantly upon sending the Bitcoin to the specified address within 120 seconds of the QR code appearing on the screen.