Here's what's going on.
I can make an educated guess about what your experiment is, but the question can be answered without knowing the exact reaction.
Notice that the student added less acetic anhydride,
The stoichiometric calculations determined that you need
This means that the acetic anhydride will most likely become a limiting reagent, since you have less than what you need.
As a result, the theoretical yield of the reaction, which tells you how much product you should expect to see for a
The actual yield, which represents the amount of product you actually get if you take into account the reaction percent yield, will be affected as well.
This happens because you now have less reactants actually reacting. The acetic anhydride will limit the amount of (presumably) salicyclic acid that takes part in the reaction.
The percent yield will not change. If the reaction ahs an
I recommend using so actual values, which I assume you have, to test how the theoretical yield, the actual yield, and the percent yield are affected by this accident.
SIDE NOTE Are you making aspirin?