I have reasons to disagree with the details and information provided by the diagram, maybe you're the one making the mistake after all.
To explain the diagram you brought up, you're saying that,

1. From your overall income, you get your discretionary income( which I agree with you)

2. From the discretionary income, you get the funds to settle your family expenses, save for future emergencies and also reserve funds.

3. And from your reserved funds, you can buy some Bitcoin.

So it's either I'm retarded as fuck and can't transcribe an obvious diagram, or you're the one who's not really getting this concept. Alright, I'll try making a diagram myself to further visualise my point, and if my idea is wrong then I'd be more than happy to take corrections because I'm always open to ideas and self development.


Here's my own illustration.

I find JayJuanGee to be quite experienced and knowledgeable in this field and so would like to invite him to give his own opinion on this (which I know he would love to) and like I said, I'm open to corrections if I find that my approach is incorrect.