zhì shǎo shì xià xiàn zuì duō shì shàng xiàn gāng hǎo shì bù duō bù shǎo

至少是下限，最多是上限，刚好是不多不少。

'At least' is the lower limit, 'at most' is the upper limit, and 'just right' is neither too much nor too little.