They've posted the site plan to the AULCC page. It's really difficult to read the elevations since they're a photocopy of the original, but there is a site data box a few pages down that lists the two phases as phase one being a 56-story 595 foot tower, and phase two being a 61-story 695 foot tower.
The elevations for both towers are using a baseline number of 100 feet, which means that you have to subtract 100 feet from whatever the height is listed as on the tower elevations.
There's also some discrepancy between the site data box and the building elevations. The building elevations show the shorter tower as phase 2, whereas the site data box is listing the shorter tower as phase 1.
The elevations for the hotel/condo tower seem to show it with just 50 floors. And it's really difficult to read, but it looks like the height is listed as 691 feet and some inches, but you have to subtract 100 feet from that number, which actually puts the height at 591 feet.
The elevations for the apartment tower are a bit more clear. The odd thing is they also show it with 50 floors instead of the stated 56. The height listed for this tower is 681 feet and either 6 or 8 inches, but you have to subtract 100 feet from that, so the height is actually 581 feet. The mechanical penthouse overruns that height for a few more feet, presumably to the 595 foot number that the site data box listed.
ftp://ftp.ci.austin.tx.us/ATD_AULCC/...is_PLAN_02.pdf