Wagner standard rung-to-rung is 12 inches.
Count the rungs, like Catturd said.
I’ve got one of those & a folding extension ladder two - they are totally distinct things ... hey may have bought an extension ladder at HD but the one in Foldspace pic via Catturd is the one I remembered being there & was probably put in place ahead of time. This thing is about to blowup. Nothing can stop what is coming!