I updated the height in the title.
If you scroll down to page 97, you'll see that it lists the average grade elevation of the site as being 513 feet 3 inches. The highest elevation they list for the roof is 698 feet 3 inches - so 185 feet. Also, that height is only to the main roof and doesn't include the mechanical penthouse. The heights are listed on the stacking plan. That actually ins't the building elevations. I'm sure that the building elevations will show the mechanical penthouse. It should probably add another 8 to 12 feet of height. I think the 179 foot 3 inches height is measuring from the entrance of the grocery section of the building.
http://www.austintexas.gov/edims/document.cfm?id=239586