The number of the days is a literal translation. New Revised Standard Version uses more idiomatic English, “the length of time.” Anchor Bible has “the amount of time.” See also New American Bible, “In all, David lived a year and four months….”

The country: better, “the countryside.” This is the same word as in verse 5, “the towns of the open country.” The sense here seems to be that David remained in the open country rather than living in any of the major Philistine cities. Compare Traduction œcuménique de la Bible “in the Philistine countryside” and similarly Nueva Biblia Española. It appears again in verse 11.

A year and four months: literally “days and four months.” On this Hebrew idiom see the comment on 1.21 (also 29.3). In some languages it may be more natural to speak of this period of time in terms of the total number of months (sixteen), as Good News Translation has done.

Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 1. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .