When your stack drops to about fifteen big blinds and below, poker stops being a game of postflop finesse. There is no room to raise, get raised, and still have chips to manoeuvre. The winning strategy collapses to two buttons: jam all in, or fold. The happy part: this corner of the game is essentially solved. Learn the jam-or-fold frontier and you will never again agonise over a nine-blind spot.

Why it collapses to two buttons

A small raise when you are short is the worst of both worlds: it commits a chunk of your stack and folds nothing out, so you get shoved on and called off anyway. Going all in fixes both problems at once.

Shoving wins the blinds and antes outright a large share of the time, and when you do get called you still have live equity. You also take away your opponent's chance to outplay you after the flop: there is no flop.
Folding risks nothing beyond the blind you already posted.

So the decision is a clean comparison: the expected value of jamming versus the expected value of folding. Pick the bigger number. That is the whole game when you are short.

Two seats, two ranges

Heads-up (the spot the puzzle drills), there are two roles, and they do not use the same range.

You shove (the small blind). You jam wide, because much of your profit comes from simply taking the blinds and antes uncontested. The shorter your stack and the more dead money in the middle, the wider you go, toward any two cards at the very bottom depths.
You face a shove (the big blind). You call tighter. Calling has no fold equity: you can only win at showdown, so you need genuine equity against the whole range that just jammed, at the price the pot is offering. This is pot odds and hand reading, all in one decision.

Every stack depth has a Nash-equilibrium threshold for each seat — the unexploitable strategy that no opponent can profit from by deviating. Note that unexploitable is not the same as optimal against a known weak opponent: versus a caller who folds too much, you can jam even wider; versus one who calls too much, you tighten. Nash is the correct starting point, not the final answer. The shape is what matters, not the 169 individual cells: pairs and aces always, then broadways, then suited connectors, and finally the offsuit junk that only the shortest stacks reach. Antes widen everything. More dead money makes a successful shove worth more, so both the jamming and the calling ranges stretch.