有这个“了”的句子通常在“句意”上有种尚未完结的感觉，还需要加上其他讯息来让句意更完整。因为这个“了”是为了特别指出某件事或某个动作的完成，而不是一个时间上的坐标。
yǒu zhè ge “le ”de jùzi tōngcháng zài “jù yì ”shàng yǒu zhǒng shàngwèi wán jié de gǎnjué ，hái xūyào jiāshàng qítā xùnxí lái ràng jù yì gèng wánzhěng 。yīnwèi zhè ge “le ”shì wèile tèbié zhǐchū mǒu jiàn shì huò mǒuge dòngzuò de wánchéng ，ér bu shì yī gè shíjiān shàng de zuòbiāo 。
When using this le, the sentence can often feel unfinished. You need more information to make the sentence more complete. The reason being, this le's specific function is to highlight that a specific action has been complete, rather than being a marker of time.