adjustment

An adjustment is a small change made to get something right. A minor adjustment, make an adjustment, an adjustment to the figures.

It implies fine-tuning rather than redesign. In finance and accounting, an adjustment is a correction to a figure already recorded. In psychology, adjustment means adapting to a new situation, and adjustment disorder is a clinical term. Note adjust, adjustable; and that a few small adjustments is what everybody says at the point where a rebuild is actually required.