How long does Poloniex register my Steem Dollars transaction?

Hi. I am a newbie in all these so please bear with me.

I read a guide explaining how to 'materialize' the Steem money to real money, and this is the easiest one I've read:

https://steemit.com/steemit/@ash/steemit-how-to-sell-steem-dollars-via-poloniex-newbie-friendly

So anyway, I went to Poloniex, registered, then transferred my Steem Dollars SBD to @poloniex. Now, it says wait for 10 minutes for the transaction to be registered, but it's about 15 minutes now (as of the writing) and there's still nothing on my Poloniex. Did I miss something?

Please kindly help. Thank you.