不到 + Number/Time + 就 + Verb
The adverb 不到 (búdào) means "less than" or "under" and is placed before a number or time expression to indicate that a quantity or duration falls below a certain threshold. It is commonly used in both spoken and written Chinese.
这个项目不到三天就完成了。
zhège xiàngmù bú dào sān tiān jiù wánchéng le.
This project was completed in less than three days.
她不到二十岁就开始创业了。
tā bú dào èrshí suì jiù kāishǐ chuàngyè le.
She started her own business before she was even twenty years old.
从这里到车站不到十分钟的路程。
cóng zhèlǐ dào chēzhàn bú dào shí fēnzhōng de lùchéng.
It's less than a ten-minute trip from here to the station.