Hello Kensuke

This is caused by a conflict with Autoptimize's CSS. You can add this custom CSS on the page, and it should be resolved:

@media only screen and (max-width: 767px) {
.amelia-app-booking #am-step-booking .am-recurring-setup, .amelia-app-booking .am-step-booking-catalog .am-recurring-setup {
box-sizing: border-box !important;
}
}

You're welcome, Kensuke

Glad I could be of assistance.

If you have any further questions or issues, please feel free to open a new ticket, and we'll gladly help.