The Key to Success

For those looking at the red 3K on Delver's Journey rep you can safely turn this in without worry.

Before turning in the quest I checked my numerical rep value (3267).
After turning in the quest I checked it again (2817).
This checks out as each threshold is 4200.

933 rep to the first threshold and 2817 beyond the first threshold totals a 3,750 rep increase (3K + 25% bonus).

You can see your progress for this rep in the Delves tab on the LFG interface. The progress bar doesn't show the numerical value but you can use the following to check it:
/dump C_MajorFactions.GetMajorFactionRenownInfo(C_DelvesUI.GetDelvesFactionForSeason())

To clear the confusion from previous posts.
It's once a week from a bountiful chest and its once per warband (can't get others with alts)

If you have the ? on your mini map saying the quest is ready for turn in but do not have a cipher key in your bags, there are three possibilities:
1)There is a bug that deletes the item from your bag like you didn't get it if your client crashes or you right click and close the application.
2) This quest is from the previous week, it sometimes deletes the cipher after reset.
3) The most likely, you got this quest and then didn't turn it in and then got it and turned it in on an alt, this will also delete the key from your inventory on all other characters as you can only do it once per week per warband.