Appointments 20 minute service not available

Here is a strange one. One of service times for some of my Providers. Take a look at the screen shot. It is open for 30 minutes but not the 20 min. Please help, I have granted access.
for site: http://massagetx.com/wb/
thanks,
matt
this may be related to some other issues in this tread. but may not: https://premium.wpmudev.org/forums/topic/appointment-not-sending-confirmation-eamils#post-912455