I presume a word had been deleted after I started the course and the count has never been updated, which will mean that I’ll never be able to complete the course.
It would certainly be nice to see this bug squashed once and for all, but in the mean time, you can try to get in touch with the course creator or a contributor and have them try a few things to force a refresh of the database. There was some more discussion on the topic here:
As an additional note to what I mention in that topic, some users have reported success in fixing this glitch by changing the course’s status to “Private”, then back to “Public”. In any approach though, it’s something that needs to happen on the creator/contributor’s end, and I’ve seen some users state that it takes a while to take effect.