In numerology, several different numbers get calculated from your name and birth date — expression number, soul urge number, personality number. The life path number is usually presented as the headline figure, the one meant to summarize the broadest strokes.
Mechanically, it's unambiguous: reduce a birth date to a single digit, with 11, 22, and 33 kept as exceptions by most Western schools. Interpretively, it opens onto a large and varied tradition, with different schools attaching different themes to each number.
The two halves of that sentence — the math and the meaning — deserve very different levels of confidence.
