In the clip, Charmaine was practicing Chinese calligraphy during filming breaks. What she wrote was:
"Brother Goon said he's treating me milk tea. But he haven't."
LOL, the Brother Goon she was referring to was 攝影大管, one of the co-director/camera in the series. He replied in his weibo in response to the video: "I'll buy tomorrow. (Cries) Feeling hurt right now..."