A funny "doesn't know the rules" situation

[Comp]

How often do you find that coaches think the DP/Flex rule means you get 10 hitters in the lineup? The opposing coach did that in our first game of the year, but we were up 23-0 when that 10th spot came up so I (and the umpire) just let it go. I kinda felt like I should've made a bigger point of it so the coach knows she got the rule wrong for the future, even though I didn't care another kid got an at bat in the game.

Ive actually only had it happen one time in a high school game. The penalty pretty stiff since it is an illegal substitution, pretty sure that coach never made that mistake again.