Many psionic abilities in the GURPS Psionic Powers book do not have a fixed cost per level.To deal with this, I used modifiers as a replacement for ability levels.You only need 1 level active at a time (i.e. you do not need Interruption_2 and Interruption_1 active, only Interruption_2).
The underscore is related to the irregular points per level of some psionic abilities.If a skill is red and says this is the problem, go to the related ability and activate a modifier to "level up" your ability.All levels 1+ fulfil this requirement.
Limited versions of psionic powers at reduced cost.These are not compatible with the delimited version the power (i.e. Take either Telekinesis talent or Psychokinesis Talent, but not both.)