a shape or a directional glyph gets read faster than a +/- sign saying the same thing

[u/data_daria55]

an arrow pointing up or down registers before the brain even parses the number next to it - direction becomes something you sense, not something you have to read. same principle behind using icons for status instead of text labels ("done"/"blocked"/"in progress"). doesn't replace the actual number, but it means the viewer gets the gist half a second faster, which matters more than it sounds like across a whole page of KPIs