What's the right box?

This may sound very stupid but I find that 600ml boxes can hold more food than I can actually eat! My mum has always cooked in "diet" way as my dad and my grandmother can't eat salt, and she is particularly picky about me getting fat (I am not at all, though) so due to that I'm used to eat very small portions. I've been searching for bento boxes that are around a 500 ml capacity but I don't find them... And I'm afraid that little "side dish" boxes (those around 250-300 ml) may be too small. Any help? I'm not sure about how to measure the capacity in a box so I have a little problem there. Or maybe the problem is not the capacity but the quantity or kind of food I put in the box. Maybe I should cut out the carbs and put more veggies? This is sooo complicated! I actually own a red 2 tier Urara box and a box that has only one tier (i like it much better). Thank you!!! *n_n*
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