70% material salvaged

It sounds like you are looking at a single material and deciding whether it has 70% of its cost or replacement cost coming from a salvaged source. If it does, it qualifies as a "sustainable purchase" and gets to count toward the total value of sustainable materials purchased for facility improvements.

For an individual material or product, the denominator is the cost or replacement cost of that item. The numerator is the % of that item's value that comes from a salvaged source, FSC source, recycled source, etc. (We've not seen a definition of an "item" but in the US we have assumed it to be a single section number in the CSI numbering system such as "096400 Wood Flooring" or "081001 Interior Doors.)

For example, assume one of the improvements is a new fitness room, where 90% of the flooring is reclaimed wood floor from a bowling alley. The total cost for new wood flooring would be $10,000. Since more than 70% of the value of the wood flooring is coming from a salvaged source, it qualifies as a "sustainable purchase" and you get to include all $10,000 in the numerator for the whole credit calculation even if you paid less for the salvaged wood.

Does that answer your question?