How do Social Security Credits Work

[rocky848]

Why does SSA say you must earn $400 dollars or more to earn at least one credit if You're self employed by using the optional method ?

[Mr. Knowitall]

Per the SSA,

A self-employed person usually has to have net earnings of at least $400 to earn a Social Security credit. However, a person with net earnings from self-employment of less than $400 may still receive credits for years in which he or she uses the optional method of reporting earnings.