The K-curve (typically 8–12× In magnetic trip) suits it for loads with moderate inrush, such as motor starters or transformer primaries, where a B- or C-curve might nuisance-trip on startup.
What the K-curve means for the application
The K-characteristic curve is the key selection parameter here. It defines the magnetic trip threshold between 8 and 12 times the rated current (80–120 A for this 10 A unit). That is higher than a C-curve (5–10× In) but lower than a Z-curve (2–3× In). For a panel builder wiring a 10 A motor starter or a control transformer, the K-curve avoids nuisance trips during the inrush event while still providing short-circuit protection. The thermal element handles sustained overloads the same way as other curves — the difference is only in the magnetic instantaneous trip point.