All IKEA base cabinet frames (including the 49" piece I think you're asking about) clock in at 24 3/4" deep, out of the box.
The catalogue/website/other source measurement of 25 1/2" for the 49 corner base includes the fixed cover panel that goes on the "dead/buried" end, and is a piece that the cabinet needs in order to properly line up in the kitchen.
Care for me to geek out about the panel and why it's there and how it works? 'Cause I can give you about 5 hours on the topic - I am
such a dork!
(If I get in to it, remind to include Kayla's take on the door/drawer configuration of the thing - it's one of those things that a lot of IKEA co-workers aren't imaginative enough to tell you about, kind of like the corner sink mod)
