Although it is odd the numbers are written like that in the first place, with kanji instead of numerals, you do get used to it pretty quickly. And yeah, every number is written individually instead of how they should be written (so ten thousand, for example, is written 一〇〇〇〇, itizerozerozerozero, instead of 万 man) but like it was stated before, it's faster to read it like that.
It's easy to remember:
〇 zero, which is... a zero,
一 Iti, one, a single line,
二 ni, two, two lines,
三 san, three, three lines,
四 yon, a box,
五 go, five, five sticks,
六 roku, six, a little man ripped in half am I screwed up if I see it like that?
七 nana, seven, it's like a really stylish t,
八 hati, eight, it's the letter ha in katakana, pretty much,
九 kyuu, nine, which is a chain letter R.