The load chart is not a suggestion. It is the legal limit. When in doubt, do not lift.
The boom buckles, or the hoist lines snap.
The angle between the horizontal ground and the boom. Higher angles generally allow for heavier lifts. How to Read a Standard Load Chart
Most modern cranes use – tabular plus range diagram.
If the ground is soft or unlevel, the crane's capacity drops. Always use outrigger pads or mats.