Subtext is the intention or meaning beneath spoken words. It is not permission to invent a secret meaning for every line; it must fit the scene, relationship, and circumstances.
The core idea
A character may say “I am fine” while trying to end a conversation, protect someone, avoid embarrassment, or test whether the truth will be noticed. Choose an intention that the script supports.
How to apply it
If a tactic fails, the character may try another: reassure, challenge, bargain, withdraw, or ask a different question. Tactics are attempts to change the situation, not decorative moods.
Try this next
Play a neutral line three ways: welcoming the other person, challenging them, or hiding relief. Keep the words identical and change the objective or tactic. Compare which interpretation is credible in context.