This can be also "several seconds" depending on context

The etymology of 초 is interesting. This should be pronounced 묘 in accordance with the Korean reading of the character 秒. The identically pronounced characters which look similar probably caused this particular reading:

• 抄
• 炒
• 吵
• 鈔
• 耖

They are all part of the same phonetic series and so by mistake, 秒 also received the same pronunciation.