Yield
The actual volume of concrete a batch produces, checked by comparing the delivered volume to the ordered volume. Consistent short yield indicates a batching problem.
What does yield mean?
Yield is verified by measuring the unit weight of fresh concrete and calculating volume from the batch weights, which is a standard test in commercial quality control. Apparent shortages are far more often caused by subgrade irregularity, over-excavation, or form deflection than by the supplier. Higher-than-expected air content also inflates volume while reducing strength.
In practice
When a crew runs short on a slab, the usual culprit is a subgrade that was low by half an inch across the whole pour.