First of all, I'd post this in the LSAT section, you mite get better responses there.
There is no legal reasoning portion of the LSAT. Perhaps you are thinking about Logical Reasoning?
The LSAT consists of four sections of approximately 25 (20-30) questions each, as well as a writing sample. The writing sample is the closest thing you get to "legal reasoning".
The sections are divided as follows:
- Reading Comprehension (1 section). Very similar to the reading comp passages on the SAT. 4 passages with around 6 questions on each one. Usually consists of, in some order, a "legal" passage, a humanities passage, and a science passage.
- Logical Reasoning (2 sections). This consists 25ish chunks of a few statements or a short passage with facts and a conclusion. There is a question about each, relating to the argument.
- Logic Games (1 section). The most feared portion of the LSAT. You get a list of items and you have to place them in a diagram, or order them in some other way, in order to answer the questions. There are 4 games on each test.
- Writing Sample. Almost never looked at by anyone. However, you're given two choices (two candidates for a job, two possible movies for a school group, something like that) and their qualifications. You have to pick a point and argue it. Both sides are right, they just want to see how you reason out your choices.