Four charts, stored once each. Not four charts in G with a note about transposing them — four charts with no key at all, which turn into concrete chords the moment you name one. Every chord on every page below is computed from the bars you can see here, and the computation is re-run against raw semitone arithmetic on every commit, so a wrong chord on this site is a failed build rather than a typo somebody eventually notices.
They are ordered by what they ask of a reader. The first has nothing on it but digits. The second divides a bar. The third moves where a chord lands without changing what the chord is. The fourth puts marks on the number itself. Read in that order they add up to the whole vocabulary; read in any order they are still four things a session actually plays.
Bare Numbers
Eight bars, ten numbers, no other mark on the page. 8 bars, 4 beats to the bar, worked through in G and again in C.
Split Bars
Two chords in one bar, and the beats that say which one gets more of it. 8 bars, 4 beats to the bar, worked through in D and again in G.
Pushes and Holds
Where the chord arrives, and where the band stops counting. 8 bars, 4 beats to the bar, worked through in A and again in D.
Minors and Slashes
The minus, a bass note of its own, and a degree the key does not contain. 8 bars, 3 beats to the bar, worked through in C and again in F.
Why so few, and why these
A hundred charts would teach less than four. The notation's vocabulary is genuinely small — ten marks, listed on the legend — and once each one has been met in a real bar, the rest is repetition at speed, which is what the drill is for rather than more examples. What a beginner is missing is never another progression; it is the second of hesitation on a mark they have seen twice.
The four here were chosen so that between them every declared mark appears at least once, and the build refuses to pass if that stops being true. That is a small guarantee and an unusually useful one: it means the legend is a description of this site rather than an aspiration, and it means no chart can quietly introduce a symbol nobody explained.