How many Fairy Tail members went missing from the guild during the timeskip? Contains spoilers for fans who have not reached the timeskip.

The story takes a seven year timeskip at the end of the Tenrou Island arc. Members who went to the Tenrou Island to participate in the S-rank exam go missing. With the 8 exam participants and their respective partners, the 3 examiners, Master Makarov, and Laxus, that would be 21 members. Is this calculation correct?
At the end of the Tenrou Island arc,


   Acnologia sinks the Tenrou Island along with all the people on it.



Mest Gryder, one of the eight exam participants, is actually a Magic Council member, and he left the island earlier anyway.
Gray's partner, Loke/Leo, returned to the spirit world earlier.
Wendy and Gajeel took their Exceed partners, Carla and Pantherlily respectively, to the Tenrou Island. 
Laxus was not a member at this time, since he had been expelled and Makarov refused to readmit him.


Taking all the above into account, altogether 20 Fairy Tail members (and Laxus) were missing from the guild during the timeskip.

List of members (clockwise in the human circle they formed, starting from Lucy and excluding Laxus):  


Lucy Heartfilia
Natsu Dragneel
Erza Scarlet
Cana Alberona
Gildarts Clive
Levy McGarden
Gajeel Redfox
Wendy Marvel
Carla
Happy
Pantherlily
Makarov
Bickslow
Freed Justine
Evergreen
Elfman Strauss
Mirajane Strauss
Lisanna Strauss
Juvia Lockser
Gray Fullbuster