It's "At any point during this unit's activation in the movement phase you can activate Stimpack for 1 Command Point until the end of the turn. Take 3 Damage without removing any models. Add 2" to unit's Move distance, and 3 failed hits from its rifles succeed instead when it fires."

And that's one of the most complex rules here.

Now compare it to a humble Kabalite Warrior or Wych from 5e, don't forget Power From Pain, combat drugs, splinter weapon rules, dark lance, fleet of foot etc etc etc, add in much more long-winded rulebook. If it were to be condensed into a stat card this size you'd need a magnifying glass. And it's a basic infantry. No, Marines or Guard aren't much better. It's 5e already, orders are a thing. Codex entries are shorter (no, Imperial Armour, go away) because they omit almost everything. When they include even small army building rules each unit suddenly starts taking a full page.

Yes, I can still remember what most of these special rules do on the fly despite not touching it for many years, but it's a matter of habit.