Confusing use of 減る


Maruko is complaining that mum is buying seaweed as a new year's present. Mum
replies:

> 「のりは食べる機会が多くて **すぐに減る** からもらったらありがたいもんなのよ。」  
>  There are plenty of opportunities to eat seaweed, and because they
> **immediately decrease** , when one receives it they are grateful.

Why do the opportunities to eat seaweed decrease? Is there some cultural
knowledge I'm missing or is my translation wrong?




What decreases is the stock on hand. In other words, Maruko's mother is saying
that, since people eat nori on so many occasions, **one's supply** runs out
very quickly, and so one is happy to receive it. Think of a big pool of
available nori that gets drained as it gets used.




What decreases is the stock on hand. In other words, Maruko's mother is saying
that, since people eat nori on so many occasions, **one's supply** runs out
very quickly, and so one is happy to receive it. Think of a big pool of
available nori that gets drained as it gets used.

