במדבר פרק א, מו
לָֹּכ ּויְהִּ יַו-הַפְּקֻדִּ ים ש ֵש -מֵאוֹת אֶּלֶּף וּש ְלש ֶּת אֲלָֹפִּים וַחֲמֵש מֵאוֹת וַחֲמִּש ִּּים:
This is curious that by all the other tribes the number of the population concludes with a complete number in the hundreds, with no tens or single units. The exception is the tribe of Gad (verse 25) which ends in a number of 50 (and thus the total of all the tribes also has a full number plus 50). The same pattern exists in the counting of the tribes in Parshas Pinchas, where all end in complete hundred units, with one exception (Reuven) which has a count ending with 30.
It is well known that in many places the numbers are rounded off (39 to 40, 49 to 50, 69 to 70, etc.). Thus, numbers are rounded off (up or down) to make a number of even hundreds. The only exception would be when the number is exactly 50, and then, the number would not be rounded either way, which is the case in this Parsha.
The difficulty remains for Parshas Pinchas, where the number count is 30, which per the previous explanation should be rounded off to the nearest hundred. Perhaps, one can learn from Parshas Beshalach (Shmos 14, 7) that Paroh sets up his army to pursue the Jews, the verse states ושלשים על כולו (establishing groups of 30). Thus, by an army, a group of 30 is an important number unit. And, thus, in Parshas Pinchas which has a greater connection to a count for military purposes, then a number of exactly thirty would not be rounded to the nearest hundred.
The importance of the number 30 is found in Tanach (Shoftim 10,4, Shmuel I 9,22, Shmuel II 23, 13) and in Gemara (Berachos 32b, Chulin 92a).
