17 = 8.
https://tricycle.org/magazine/noble-eightfold-path/
Within the fourth noble truth is found the guide to the end of suffering: the noble eightfold path. The eight parts of the path to liberation are grouped into three essential elements of Buddhist practice—moral conduct, mental discipline, and wisdom. The Buddha taught the eightfold path in virtually all his discourses, and his directions are as clear and practical to his followers today as they were when he first gave them.
The Noble Eightfold Path
Right understanding (Samma ditthi)
Right thought (Samma sankappa)
Right speech (Samma vaca)
Right action (Samma kammanta)
Right livelihood (Samma ajiva)
Right effort (Samma vayama)
Right mindfulness (Samma sati)
Right concentration (Samma samadhi)
Practically the whole teaching of the Buddha, to which he devoted himself during 45 years, deals in some way or other with this path. He explained it in different ways and in different words to different people, according to the stage of their development and their capacity to understand and follow him. But the essence of those many thousand discourses scattered in the Buddhist scriptures is found in the noble eightfold path.
It should not be thought that the eight categories or divisions of the path should be followed and practiced one after the other in the numerical order as given in the usual list above. But they are to be developed more or less simultaneously, as far as possible according to the capacity of each individual. They are all linked together and each helps the cultivation of the others.
These eight factors aim at promoting and perfecting the three essentials of Buddhist training and discipline: namely: (a) ethical conduct (sila), (b) mental discipline (samadhi) and (c) wisdom (panna). It will therefore be more helpful for a coherent and better understanding of the eight divisions of the path if we group them and explain them according to these three heads.