An overflow: auto box with a max-height of 400pt whose six lines fit under the cap: it breaks between its lines.
Fits line 1
Fits line 2
Fits line 3
Fits line 4
Fits line 5
Fits line 6

After the box.

An overflow: hidden box with a max-height of 96pt and twenty lines: it breaks after the third line, shows five more on the next page, and clips the rest.
Capped line 1
Capped line 2
Capped line 3
Capped line 4
Capped line 5
Capped line 6
Capped line 7
Capped line 8
Capped line 9
Capped line 10
Capped line 11
Capped line 12
Capped line 13
Capped line 14
Capped line 15
Capped line 16
Capped line 17
Capped line 18
Capped line 19
Capped line 20

After the box.