At the End of Fiscal 2021 Less than 12 months Greater than 12 months Total Unrealized Fair Value Loss Fair Value Unrealized Loss Fair Value Unrealized Loss U.S. government treasury notes $ 8,301 $ (1) $ — $ — $ 8,301 $ (1) Corporate debt securities 32,996 (33) — — 32,996 (33) $ 41,297 $ (34) $ — $ — $ 41,297 $ (34) Total Realized gains or losses on sale of marketable securities were not significant for all periods presented. Other Financial Instruments We measure the fair value of our Notes on a quarterly basis and we determined the fair value of the Notes at the end of fiscal 2020 and 2021 to be a Level 2 measurement due to its limited trading activity. Refer to Note 7 for the net carrying amounts and estimated fair value of the Notes at the end of fiscal 2020 and 2021. 73