How much exactly, is a tenth of an Eifah?
Rashi: 1 Eifah = 3 Sa'ah; 1 Sa'ah = 6 Kabin; 1 Kav = 4 Lugin; 1 Log = 6 egg-volumes. Consequently, a tenth of an Eifah = 43 1/5 egg-volumes, which is the Shi'ur for taking Chalah and the Shi'ur of Menachos.
Why does the Torah insert this Pasuk here?
Ba'al ha'Turim: To teach us that, after Moshe's death, they continued to eat the Manna until they brought the Omer on the sixteenth of Nisan.