文本来源:佛山外国人学中文 首选爱德华国际汉语

七上八下(qī shàng bā xià)
七(qī) stands for seven and八(bā) for eight. 七上八下(qī shàng bā xià) is often used when “someone is very upset or anxious and feels ill at ease”. For example,
他就感觉心里七上八下。
tā jiù gǎn jué xīn lǐ qī shàng bā xià.
He is very anxious.

十拿九稳(shí ná jiǔ wěn)
十(shí) is ten and 九(jiǔ) is nine. You can use 十拿九稳(shí ná jiǔ wěn)when you are quite certain of something. For example,
他学习很好,考进前三名是十拿九稳的事。
tā xué xí hěn hǎo, kǎo jìn qián sān míng shì shí ná jiǔ wěn de shì.
He studies very well, so it is certain that he will be placed in the first three spots in the exam.

十全十美(shí quán shí měi)
十全十美(shí quán shí měi) means perfection. For example,
新生事物在刚产生时,并不都是十全十美的。
xīn shēng shì wù zài gāng chǎn shēng shí,bìng bù dōu shì shí quán shí měi de.
It is impossible for new things to be perfect.
More Numerical idioms for you:
一目十行(yī mù shí hang): cover ten lines at one glance; quick in reading.
一言九鼎(yī yán jiǔ dǐng):keep one’s promise.
一心一意(yī xīn yī yì): be preoccupied with.
三心二意(sān xīn èr yì):be of two minds
四通八达(sì tōng bā dá):accessible from all directions.
九牛一毛(jiǔ niú yī máo):a drop in the bucket.