Thats the phone id model that we can activated. You can verify if a certain phone can be activated here or not by accessing the following link and adding the DEC/MEID to check:
Not sure if you still need to know this, but yes, you can buy a S9 directly from Samsung and use it with boost, even the ones with higher gigs. I currently have a 128gb, and it works well. Make sure you get the SIM card SIMOLW406TQ, which is compatible with the s9/s9+. Don't order a sim card from customer care, because they will send out the wrong sim card. I speak from experience, they sent me two sim cards for the s8. Also, don't listen to the reps in customer service or here that try the claim you can't use an unlocked s9/s9+. They are just trying to make you buy from boost directly and have a sale in their pocket or they have no idea what they're talking about. Hope this helps.