The character is correct in the vocabulary sample sentences (page 3) but not on the last page(page 5)
慢 vs 瞒 for the same phrase
page 3
哎哟,你怎么这么慢!
Aiyōu, nǐ zěnme zhème màn!
Jeesh! How can you be so slow?
page 5
哎哟,你怎么这么瞒!
āiyōu, nǐ zěnme zhème mán!
"Jeesh! How can you be so slow?"
Courtesy of my TAFE teacher (had the lesson notes open in class)