If you answer both questions correctly, you will find out the numerical code to decrypt this paragraph from Minerva McGonagall's letter:
Aopz alyypisl jpyjbtzahujl pz jhbzpun thuf wyvisltz huk huuvfhujl ivao htvun zabkluaz huk alhjolyz, zpujl aol thnpj dvykz ohcl av il ypnoa mvy lhjo ahzr huk tbza il wyvuvbujlk dpao nyhtthapjhs jvyyljaulzz huk hizvsbal wyljpzpvu.