How do we find 300 years since Yisrael conquered Sichon?
Rashi, citing Seder Olam 12: Yehoshua reigned for 28 1 years; there is no verse for this. Osni'el reigned for 40 years (3:11), including the years of Shibud under Kushan Rish'asayim (3:8). Ehud [was Shofet] for 80 years (3:30), including the 18 years of Shibud under Eglon (3:14). Devorah [was Shofet] for 40 years (5:31), including the years of Shibud under Yavin (4:3). After this were seven years of Shibud under Midyan (6:1), and Gid'on [was Shofet] for 40 years (8:28). Avimelech reigned for three years (9:22), Tole'a reigned for 23 years (10:2), and Ya'ir for 22 years (10:3), but one year counted for both of them (for each, a partial year was counted as a year of his reign). There were 18 years of Shibud under Amon - in all, exactly 300.
Radak citing Seder Olam 12 2 : Yehoshua reigned for 28 years, Osni'el for 40, Ehud for 80, Devorah and Barak 40, Gid'on 40, Avimelech three, Tole'a 23, and Ya'ir 22. These 276 years include all the years of Shibud. After were 18 years of Shibud under Amon, and six years of Yiftach 3 - in all exactly 300.
The Ibn Ezra and Ramban (Shemos 33:11) say that he was 56 at Yetzi'as Mitzrayim, i.e. he died after the 14 years of conquest and division. If so, there were only 286 years! Perhaps they hold that Devorah's years do not include 20 years of Shibud under Yavin. Either (a) Yiftach was not precise (it was really 306 years), or (b) Amon had claimed the conquered land six years earlier, eight years into their Shibud, or (c) the eight reigns and three Shibudim count a partial year like a full year; the 11 partial years comprised only five years, or (d) the seven years under Midyan are included in Gid'on's years, and (like Seder Olam says) Yiftach replied so in his second year. (PF)
Seder Zemanim (a Perush on Seder Olam): The Radak had an errant text of Seder Olam.
Radak (18:1): Counting Yiftach's six years towards the 300 helps to resolve the years of the Shoftim and kings from now until Binyan Beis ha'Mikdash 140 years after this. (Why does he say that Yiftach sent to Amon at the end of his reign? The verses imply that he sent right after he was appointed! Why didn't Ziknei Gil'ad complain during the six years that Yiftach did nothing?! Perhaps he spent the six years recruiting an army. In our text of Seder Olam, the seven years of Shibud Midyan are not included in Gid'on's years, and Tole'a and Ya'ir each ruled [partially] in one year, but it was counted as a year for each, and Yiftach sent in his second year. The 300 years finished when he was appointed! Perhaps he was appointed e.g. in Adar, and Nisan was already called his second year; see Rosh Hashanah 2a. - PF)
