Start with the exact profile and series
A size chart only makes sense when the section type and series are clear. An angle, a hollow section and a pipe can share similar numbers while describing different shapes. Keep the designation from the drawing or manufacturer table.
Read dimensions in the right order
Angles are commonly written leg × leg × thickness; flats use width × thickness; plates use thickness, width and length; hollow sections use outside width × height × wall thickness. Pipes may be specified by outside diameter or nominal bore, so include the notation used in your drawing.
Treat a published range as a reference
A manufacturer may publish minimum and maximum dimensions without making every combination between them. A size chart also does not confirm present stock, grade, mill, or delivery. Submit the exact size and make requirement for confirmation.
Use the project specification for structural work
A catalogue lists available dimensions; it does not determine whether a section is suitable for a span or load. Follow the project drawing or a qualified structural engineer's specification.