Number + も/Number + しか + negative
You can add も to the number word, when you want to say "as many as"
Ex: きのうのパーテイーには学生が二十人も来ました。(As many as twenty students showed up at the party yesterday.)
You can add しか to the number word and turn the predicate into a negative when you want to say "as few as" or "only"
Ex: 私は日本語のじしょをいっさつしかもっていません。(I have only one Japanese dictionary.)