A Missed Luxury (Dramatic Irony)
When Claudia starts to scrounge and save her allowance in order to fund her running, she concludes that "The fact that her allowance was so small that it took her more than three weeks of skipping hot fudge sundaes to save enough for train fare was another example of injustice" (pg. 6).
This is ironic because having a small allowance and skipping hot fudge sundaes is not generally considered an injustice in a world where millions of children go hungry – something that the audience recognizes, but Claudia does not.