Disappointing dyno results

VE is Volumetric Efficiency.
its the amount of air consumed (or trapped) in the cylinders compared to the cylinder volume.
At low rpm the valve overlap and slower airflow results in lower amount of air mass in the cylinder than theoretical.
Peak VE is where the engine combination is most efficient.
A decent engine ought to hit close to 95% at some rpm. A desktop dyno can point to specific VE one ought to expect from an engine combination.
A really good build can hit or exceeed 100% in a limited rpm range, usually high rpm, when the induction and exhuast can support the design. This is race engine territory.