I've just been browing my KO2001 ebook, and have noticed there are no examples for the first set of kanji - number.

Obviously I already know the basic number readings for them, but readings like "first", "first of the month", "one apple" etc I don't know.

Is this a problem, or will I learn them in context whilst going through the book?

I believe most of those are included in later KO2001 sentences, as well as smart.fm. (Or both via iKO, as I think I'll refer to the iKnow[smart.fm]/KO2001 lists).

There are sentences with numbers. (fair enough, they don't use kanji but..)
2月15日は月曜日だ。

Wow that was an interesting sentence...

KO2001 doesn't explicitly include example sentences for numbers. But let me tell you, it did wonders for my ability to quickly read and speak numbers. Lots of sentences have numbers for prices or dates - the types of numbers you are likely to see most often. Before beginning it would take me AGES to read out a number, whereas now its no problem. (Interestingly even after 5 years of Indonesian in high school [my pre AJATT days-so I was just doing classwork] I still hadn't had enough exposure to be as comfortable with their numbering system as I am now with Japanese's)