The alarm clock at home shows that it took Xiao Liang four hours to go out and come back, but he only stayed in the library for one and a half hours, so the total time for him to go back and forth was two and a half hours, which calculated that it took him one hour and fifteen minutes to get home from the library. Xiao Liang arrived at the library at 8: 50 and went home after reading for an hour and a half. Then the time when he left the library should be 10: 20. It takes one hour and fifteen minutes to get home, so the correct time for him to get home is 1 1: 35. So he wants to set the time to 1 1: 35 to make the alarm clock on time.