Explanation

Fajr: 2 Rakat Sunnah, then 2 Rakat Fardh.

Dhuhr: 4 Rakat Sunnah, then 4 Rakat Fardh, then 2 Rakat Sunnah, then 2 Rakat Nafl (optional).

Asr: 4 Rakat Sunnah, then 4 Rakat Fardh.

Maghrib: 3 Rakat Fardh, then 2 Rakat Sunnah, then 2 Rakat Nafl

Isha: 4 Rakat Sunnah, then 4 Rakat Fardh, then 2 Rakat Sunnah, then 2 Rakat Nafl (optional), then 3 Rakat Witr Wajib (obligatory, second to Fardh), then 2 Rakat Nafl (optional)

There are the following 17 Farz in Namaz

2 Farz = Fajr
4 Farz = Zuhar
4 Farz = Asar
3 Farz = Magrib
4 Farz = Isha
17 Total Farz