It is a deduction that would be applied to an individual's income. It would reduce the amounts at the marginal tax rate that the individual would face. That would be the difference from a credit set, let's say, at 15%. If you have a credit at 15%, it reduces the amount you owe, as opposed to a deduction that reduces at the margin.
Every individual would have a different benefit here. It depends on your marginal tax rate. It's not based on a given percentage, as credits usually are.