Is this over summarization using BGP?

I'm in a class learning BGP currently. The instructor asked us to summarize these hypothetical routes without oversummarizing. I summarized them to 214.1.0.0/19. He says this is not correct, but I went to a route summary calculator and it says it is? Any help/explanation is appreciated, thank you!

Routes to summarize:

214.1.2.0/24

214.1.3.0/24

214.1.4.0/24

214.1.5.0/24

and so on to 214.1.20.0/24