But you have not activated any level.
Maybe it is covered elsewhere, but under Optimization Negative traits.
"When a character has a “partial” negative Trait at the time
he decides to optimize the character, the optimization process
adds XPs to the character’s XP Pool by adding negative XPs to
the Trait (as opposed to spending positive XP the character
may not have to “buy off ” a partial negative Trait)."
"However, this form of optimization is limited to attaining only the nearest
“activated” level of the Trait (the point where its negative XPs
round off the Trait to its next lowest level of game play effect).
For example, if the character has received –125 XP in Glass
Jaw—a 3 TP Trait that costs –300 XPs to activate—then it will
take an additional –175 points to optimize the Trait, adding
175 XPs to the character’s XP Pool in the process."
Again the real issues here is the conflicting descriptions and rules.
While I don't doubt that "just buy it off" is the intent. The rules as written tend to pull you in multiple directions on this with rule and example conflicting with each other and on some cases themselves.