Hi Sarah,
Here is how it looks like on a iPhone 6:

Is it different when you look at it? If so, could you make sure you have cleared your cache? And could you tell me which device/browser you are using?
If the problem comes from the text area which you think is not wide enough, then you could add the following snippet, still in Appearance > Customize > Additional CSS:
@media only screen and (max-width: 800px) {
.tribe-event-tickets-plus-meta textarea {
width: 100%;
}
}
Please let me know how it goes.
Cheers,
Jeremy