If you answer both questions correctly, you will find out the numerical code to decrypt this paragraph from Minerva McGonagall's letter:
Di ocznz xdmxphnovixzn, ocz Hdidnomt ja Hvbdx cvn wzzi diajmhzy wt mzgdvwgz njpmxzn ocvo nopyzion ja xgvnndxvg gvibpvbzn amjhooczhkmznodbdjpnunxcjjgn