They mean nothing. It's been officially stated by Roland on a few occasions(including when they first started) that they don't mean anything. First we had a life bar that was gradually decreasing, which meant nothing. That was basically playing a joke on the life bars people saw in the test images that caused a huge controversy. And of course [not] everyone thought it was an exact scientific countdown of the progress until release.
Then it went away and was replaced by the simple, obvious and true message that A17 would be done when it was done. Of course [not] everyone found that EXTREMELY offensive and demeaning to the paying customers and demanded that we all be treated better. Between that and some thread banter about how it's hard to tell when people are joking or being sarcastic without smileys, we then got some smileys added to the message to explain the apparently difficult concept that "it's done when it's done" means just that and not an attempt to insult anybody.
That gradually morphed into the slightly more accommodating phrase we have now and the emojis along with it. Which of course [not] everyone believes to be an exact scientific representation of what is happening with A17 progress and a countdown to the moment it will be released. In another week or two it will probably change into random movie quotes or something.
TL;DR - It's just a way for Roland to have fun and play with the forum regulars, and annoy the people looking to get annoyed. It officially means nothing. It COULD secretly mean something. But it probably means nothing. Unless it does.