Divination is heck of a lot like Googling. You can put in a search term as concise as possible. The better the query, the better the search results, usually... Though sometimes you may need to go through a few pages of BS results to get to the actual gold you are searching for. Sometimes what you were looking for doesn't even exist (or you're using the wrong terms, types of queries).. and so you have to think out of the box to even FIND the actual information you really need.
Much less decipher.
I always think of divination as basically that, the act of searching for knowledge. Sometimes it turns up immediate results. Sometimes it requires a little bit more introspection, sometimes personal walls and biases need to be dropped (Hello objectivity!) and other times we live in a filter bubble of our own creation, and whether we realize at a deeper level or not (subconsciously), when we ask our queries sometimes we at the heart of our queries are hoping that the cards will find and destroy this filter bubble, therefore freeing us from being chained to certain redundant answers regarding stagnant areas in our lives...
For me, I take divination beyond that level, it is a spiritual and self-maintenance process, something I use to "clean house" and a way to manage the amount of noise I deal with daily with being so sensitive to people's "stuff". I use it to separate my stuff and their stuff... to me, this makes readings more objective. For others, they may be holding onto other ideas of "their stuff" that may have become dated and as such, the readings can seem more like "Malarkey" until your sense of self-awareness has caught up...
Anyway
TLDR, the quickest answer to your question... being able to discern when the answer has shifted from the query involves a little of 1) self-awareness)... 2) having an already built up of a library/internal vocabulary (aka dialogue) with your cards and 3)... the most important... PATIENCE to decipher the reading
in full.
For me, I use reversals for this purpose. If I can't understand the "hidden" juggernauts lurking beyond the reversals, then I'm likely not going to finish the process with just that reading. It may require more readings to actually get the message down, but in general, when you feel you're done, you're probably done...you fulfilled the purpose of that reading. It may not be for the original purpose you thought it was for, especially if your internals are going through a bit of remodeling
, but it's what you needed to move forward from that point.