How many deflection arrows are used for 18 lb bow?

Professional advice is that 30 kg needs an arrow with 700 deflection, so it needs 420 deflection to calculate 18 kg.

Deflection refers to the maximum deformation of flexural members such as beams and trusses under load, which is usually expressed by vertical Y axis. Traditional bridge deflection measurement mostly adopts dial indicator or displacement meter to measure directly. The smaller the number of pounds, the higher the arrow deflection, the harder the arrow, and the smaller the number of pounds, the softer the arrow.