I believe it should be SBD/STEEM. Right now the internal market tool is showing that it costs around 1.29 SBD to buy 1 steem and they indicate that using SBD/STEEM. Your tool says it costs 1.29 STEEM to buy 1 SBD, but that can't be right because 1 STEEM is worth more than 1 SBD. So if your tool is showing how much 1 steem will cost in SBD, the units should be: SBD/STEEM. I read the / as PER: SBD PER STEEM.