This is the 7725th most frequent Japanese word.
収まっ
The Japanese word "収まっ" means "to fit," "to settle," or "to be contained," depending on the context.
収まっ indicates here that the documents were contained or accommodated within the box.
その箱には書類が収まった。
The documents fit into the box.
In this context, 収まっ is used to describe the act of emotions, specifically anger, calming down.
彼の怒りはすぐに収まった。
His anger subsided quickly.
収まっ is used here to mean 'settled' or 'subsided,' referring to the state of the storm calming down.