That was likely a warning (displayed in orange; errors are displayed in red) that the ga function thinks you did something wrong but it knew how to compensate and proceed.
Let's say you were trying to optimize a problem with three parameters, say quantities of three different foods you eat. You want to minimize the amount of calories you take in while having constraints on the amount of sugar, sodium, and various vitamins. You can't eat negative amounts of those three foods so you set lower bounds of [0, 0, 0, 0] on the three foods.
MATLAB knows what the first three 0's in the lower bounds are, but it doesn't know if you accidentally typed an extra 0 or if you meant to optimize a problem with four foods. It assumes the former and just ignores the last 0, but it issues a warning so if you meant the former you can correct the problem formulation..
