Why does it say "u'Min ha'Ir..."?
Radak (Melachim II, 25:19): Everything mentioned above, he took it from the Beis ha'Mikdash.
What is the meaning of "Seris"?
Refer to Melachim II, 8:6:2:1.
Here it says "seven from those who see the king." In Melachim II, 25:19, it says five!
Rashi: Two of them were not as great as the five, [therefore they are not counted here].
Radak (Melachim II, 25:19, citing Yerushalmi Sanhedrin 1:2): Here it includes two scribes of the judges.
Malbim (Melachim II, 25:19): First, he found five. Later he found another two, and there were seven.
What is the meaning of "ha'Matzbi Es Am ha'Aretz"?
Rashi: He knows for each city the number of men it brings to the army
Radak (Melachim II, 25:19): People go out to the army according to his command.