They're presumably saying that's the income needed to service the mortgage (where what most people call the mortgage payment includes escrows for insurance and property taxes, on top of the literally mortgage principal and interest components).
That still feels like a fair over-estimated amount to me, but I think that's what they were getting at. (It could also be a figure of the amount needed to qualify for a mortgage on a place with some amount of downpayment.)
It could be an overestimate, it could be an underestimate, or for a specific family buying a specific home it may be spot on. It is kind of like saying that it costs $5,000 to build a software application. That statement is true, but meaningless.
That still feels like a fair over-estimated amount to me, but I think that's what they were getting at. (It could also be a figure of the amount needed to qualify for a mortgage on a place with some amount of downpayment.)