When you get the results back be sure to multiply the Ward Labs reported 'SO4-S' value by 3 to convert it into 'SO4'.
Ward Labs primarily caters to farmers, and they only want to know how much sulfur is in their water. So Ward Labs only reports S (sulfur) as derived from SO4, and their shorthand for this is SO4-S. It just so happens that the molecular weight of sulfur is 32, and that of oxygen is 16, which since there are 4 of them 4 x 16 = 64. Thus the entire molecule has a molecular weight of 32 + 64 = 96. And 96/32 = 3 (which is where the 3X factor comes from)
I would recommend you collect/test whatever water you're going to be brewing with. I collect my water from my kitchen faucet, which has an under-counter water filter, so that's what I sent in for testing.