There are 2 red hands. The big one is a chronograph hand. It times seconds when you operate the chronograph (stopwatch) function. The other tracks hours (I think - can't really see properly).
Ah, sorry, small picture and didn't spot that there were two big hands. I'm not that familiar with this complication, but believe it's to measure the split time, i.e. so you can keep the chrono running and measure intervals. The instruction manual for this calibre is this one I believe: https://secure.eta.ch/CSP/DesktopModules/ViewDoc.aspx?tabindex=2&tabid=28&DocId=306&DocType=DT