Note that in addition to the Saturday morning service reading, the beginning of the following week's Torah portion is chanted during the Saturday afternoon service and during Monday and Thursday morning services. This public reading of the Torah (called keriat HaTorah) is a religious ritual, distinct from the study of Torah, or talmud Torah.
A Jewish leap year contains 54 weeks, but a non leap year has only 50 weeks (a leap-year adds an additional month (called Adar II) to the usual 12). During the week of Passover and the week of Sukkot, different Torah portions are read, so that leaves 52 weeks for the 54 readings (2 weeks have double portions), and on non leap years only 48 weeks for the 54 (6 weeks have double portions). I hope that makes sense; if you are a bit muddled, always consult a good Jewish Calendar.
Note: In case you're interested, a year is a Jewish leap year if the number year mod 19 is one of the following: 0, 3, 6, 8, 11, 14, or 17. You can use a scientific calculator with the mod() function to determine the result.