This can't be added to the IFC calculator in the sense that Seachem does not provide any information on how much any given dose raises KH or PH. In fact they simply tell you to keep adding until you get the desired PH. Right. So this looks to me that this is merely Sodium Carbonate or maybe Potassium carbonate although they claim "is a blend of carbonate salts". Since Seachem decided to delete the SDS of that products for reasons unknown to me, I had a look at a similar product from Fritz - Fritz Rift Lake Cichlid Buffer - and the SDS of that product only mentions Sodium Carbonate...
This makes it rather simple to solve as all you need is to choose among any of these 4 compounds and proceed the same way Seachem advices. Keep adding until you get your desired PH
This one although Seachem provides the guaranteed analysis which makes it easier for us, we don't have all the compounds they list in the IFC calculator. I have added it anyway but I will run it by @zeus first see what he says. I am not sure this will be in the release though.