These twenty proximate emotions
beginning with indignation,
are said to be

the proximate factors of instability,

because they are very close
to the basic emotions or associated with them.

Moreover, they must also be known individually as to their relationships,
for instance,
whether the proximate factors of instability, indignation,
is close to or associated with the basic emotion anger.
Such things are made clear in the Abhidharma texts quoted many times throughout the text.