Complex sentence: Using a "Rule of Thumb" the reduction in Va will be half the percentage reduction in aircraft weight; for example if, with only one person on board, weight is 16% below MTOW then Va is reduced by 8%.
Split into simpler sentences: Using a "Rule of Thumb", the reduction in V A will be half the percentage reduction in aircraft weight. For example if, with only one person on board, weight is 16% below maximum takeoff weight, then V A is reduced by 8%.