A title of two characters
Brevity has a floor. This title sits under it.
What a short title loses
No other text under your control carries the weight the title does. Two characters hand that space back unused. They cannot hold the words people type into a search box, they say nothing about the page, and they offer no reason to pick your result over the ten sitting next to it.
The range that works
Most guidance lands between 30 and 60 characters. Inside that range you can name the topic, match the phrasing searchers type, and still fit a small hook. Think one clear phrase. A single word wastes the slot, and a full sentence spills past the visible width.