I took another trade for GSK options today, and I inadvertently put the wrong expiration date. It should be the June 27 expiration. I updated it just now on the site.
If you already bought the June 20, you can consider simply closing it at the current price and then immediately buying the June 27 at the current price.
So sorry for the confusion and thanks very much for your patience!
If you have any questions or feedback, I'd love to hear from you.