They are dollar signs...which is misleading since all payouts are in steem (which can be all SP or SP& SBD).
That is one of the reasons why I feel there will be a ton of interest as the price of STEEM moves higher...the rewards are the same, people just think they are getting more (which they are if they convert back to USD). Nevertheless, people on the outside looking in will see the dollar amounts and go gaga over it.