Pretty sure a secure counts as both. Best way to confirm is to unlock one item, and then do the secure and see.
Right ... which is why it should be noted that both the number of locked down and secure containers are max-1 and yet I'm still not able to secure the container.
Thanks to GM Brenna for helping me work around this bug. The workaround is as follows (initial state: lockdowns=max-1, secures=max-1): - release a locked down item (thus making the locked down item count max-2) - secure the container (secures=max, lockdowns=max-1 now) - re-lock down the item released in the first step (secures=max, lockdowns=max)
I had the same issue once I unlocked something then it let me secure and lock the one thing back down