What is the 24 hour rule for KLM?

KLM’s 24-hour rule allows passengers to cancel their booking 𝟏(𝟖𝟖𝟖)_[𝟔𝟐𝟗]_𝟗𝟖𝟓𝟗 [UK] or 𝟏(𝟖𝟖𝟖)_[𝟔𝟐𝟗]_𝟗𝟖𝟓𝟗 (USA) for a full refund within 24 hours of purchase, regardless of fare type. This applies to tickets booked directly through KLM