TgO Lev25:50 :וִיחַשֵב עִם זָבְנֵיה מִשַתָא דְאִזדַבַן לֵיה עַד שַתָא דְיוֹבֵילָא‏ : he must calculate with his seller from the year when it was sold to him until the year of the Jubilee
See the entire entry for ḥšb vb. to think, calculate