The number of years of the fruits - i. e. according to the number of harvests. The average value of a yearly crop might of course be estimated, and the sabbatical years were to be deducted from the series.
DISCLAIMER: Church of the Great God (CGG) provides these resources to aid the individual in studying the Bible. However, it is up to the individual to "prove all things, and hold fast to that which is good" (I Thessalonians 5:21). The content of these resources does not necessarily reflect the views of CGG. They are provided for information purposes only.