The instructions are all there, but can [the reader] look at a quote like this and make sense out of it?
"Breathing in long, he discerns, 'I am breathing in long'; or breathing out long, he discerns, 'I am breathing out long.' Or breathing in short, he discerns, 'I am breathing in short'; or breathing out short, he discerns, 'I am breathing out short.' . . .
Seems to be rather straightforward to me. If people try to make more out of the simple instruction given in the discourse, it becomes like "putting legs on a snake." That is, fabricating something from something that isn't there in the instruction, but is perhaps only implied in the mind of the reader because of imperfect (or conditioned) perception.
When you look at the instruction in light of the simple process it asks one to observe (the length
of the in or out breath), you begin to see that what it is asking the practitioner to do is to become aware of the precise goings-on of the breath, that is, to be so mindful of the present moment's activities that one can clearly observe the simplicity of the moment. This is the first step in the process of training the mind to be able to observe even finer and finer (more subtle, if you will) transformations or evidences of phenomena. In other words, if one is able to quiet the mind enough to be able to follow something as simple and present in one's experience as the gross length of the breath, then he will be able to eventually observe other details that aren't as grossly available to the mind's perception, such as the three characteristics of existence (impermanence, unsatisfactoriness, and impersonality).
"The gift of truth exceeds all other gifts" — Dhammapada, v. 354 Craving XXIV