Number + 秒
秒 (miǎo) is the classifier and unit of time meaning "second." It is used to express very short durations of time, often emphasizing quickness or immediacy in storytelling and everyday speech.
请等我几秒,马上就好。
qǐng děng wǒ jǐ miǎo, mǎshàng jiù hǎo.
Please wait a few seconds, I'll be done right away.
这个视频只有三十秒,很快就看完了。
zhège shìpín zhǐyǒu sānshí miǎo, hěn kuài jiù kàn wán le.
This video is only thirty seconds long, so it's very quick to watch.
短短几秒之内,一切都变了。
Duǎnduǎn jǐ miǎo zhī nèi, yīqiè dōu biàn le.
In just a few seconds, everything changed.