Why does it say that the border is Yotzei?
Rashi: Whenever it says that the border Yatza, it juts out or recesses inwards. Here it jutted out and went south of Ma'ale Akrabim. The same applies when it says Nasav or Ta'ar. 1
Malbim: Nasav means that the border turns perpendicularly; the two directions form a Dalet (perhaps rotated 90 or 180 degrees). Ta'ar means that the border surrounds it on three sides, and resumes to go straight, like initially.
Here it says "v'Yatza El mi'Negev l'Ma'ale Akrabim." In Bamidbar (34:4), it says "v'Nasav
Malbim: Ma'ale Akrabim was south of the strip coming out of the sea; the border descended on a diagonal (southwest) to include it, therefore it says here v'Yatza. The border then turned (to go northwest); the city was within the border on two directions this justifies "v'Nasav" 1 .
Bi'ur ha'Gra: V'Yatza always means to go on a diagonal, and after the border widened, it returns to go straight. V'Nasav always means that the border widens only at that place.
What is Tzinah?
Rashi: It is to Tzin. The suffix Hei is like the prefix Lamed.
Why does it say sometimes "v'Alah", and sometimes "v'Yarad"?
Rashi: Going from the east towards Yerushalayim, [the land] ascends, and past Yerushalayim it descends. From here they learned that Yerushalayim is higher than the rest of Eretz Yisrael. Yerushalayim is not mentioned here, for it is on the northern border of Yehudah, and here it discusses the southern border.
Here it says "v'Alah mi'Negev l'Kadesh Barne'a." In Bamidbar (34:4), it says "v'Hayu Totz'osav mi'Negev l'Kadesh Barne'a"!
Malbim: V'Hayu Totz'osav means that the border ended there, or there the deviation from straightness ceased, and it returned to be straight. Here, it jutted to the south to include Ma'ale Akrabim, Tzin and Kadesh Barne'a, and now it returned [to go due west]. 1
Malbim: In Bamidbar there, it says that the border went straight to Chatzer Adar. Here the Navi was concise, and relied on what is written in the Torah.
Where are these cities?
Rashi: They are the southern border from east to west, until the sea (verse 4).
QUESTIONS ON RASHI
Rashi writes that Kadesh Barne'a is within the border of Yehudah. How can Moshe have sent spies from there? He never entered the land!
Refer to Bamidbar 32:8:1:1 and the note there.