I couldn't understand 搞不懂

I participated in a two-day professional training course. After the class, one thing still puzzled me.
In the first day morning, after the service staff completed her brief introduction of that day's first lecturer, on leaving the audience hall she stretched her hand to turn the air-conditioner temperature adjusting button on the wall, just besides my seat.
I noticed the indicator was pointing at below 10 degree Celsius. I thought perhaps that button might be as inaccurate as most of the hotel room temperature adjusters. So it's fine.
But I started to feel cool, that's my fault, because I was only wearing a T-shirt, without carrying extra cloth.
When the first session was over, some audiences were putting on their extra coats.
When the second session began, the same staff introduced the second lecturer, and then on her leaving the hall she stretched her hand to turn the temperature button again. This time, it pointed at below 5 degree!
I didn't know if her action belongs to their standard operation procedure, or if she'd ever worked in a morgue before.
I knew my headache would be inevitable that night.
For 'public welfare' I turned the button to point at just above 20 degree, and kept it at the same degree during the second day, and no one was adding on or taking off their clothes since then, and it seemed nobody was napping too.

參加了二天的專業訓練課程, 課程結束後還有一件事搞不懂.
第一天早上服務小姐引介了第一位講師後,在離開講堂之時伸手調了冷氣的溫度旋鈕,就在我的座位旁邊的牆壁上.我看了一下,溫度指針指在攝氏10度之下,心想這溫度調節鈕可能和大部分飯店房間裡的一樣不準確,應該沒什麼關係吧.
不過我已開始覺得冷了,這是我的錯,因為我只穿T恤,沒多帶衣服.
第一節下課後,許多人便穿起了外套.
第二節課開始了,該服務小姐引介完第二位講師,離開時又伸手去調那個溫度旋鈕,這次指在五度之下.
我不知道她這個動作是不是她們的標準作業程序之一,還是她以前曾經在太平間工作過.
我想晚上我一定會頭痛的.為了'公眾福祉',我把旋鈕轉到20度以上,第二天也一直維持在那溫度,自此就沒有人再穿穿脫脫了,好像也沒有人打瞌睡.