when fully saturated after an irrigation... Understand that the values you see are not entirely accurate. So, this will be more useful to you after you form a good familiarity with a baseline while the plant is healthy and happy.... if it normally reads a bit higher than you would expect with excellent health and growth, then that is the bsaeline you want to stay near in future. You need to learn a healthy baseline before assuming what it is.
Any sort of evaporation that has occured will increase EC readings. Soil readings are just wonky to start. Too many possibilities of inconsistent readings etc. Probably best to collect samples from specific areas in a consistent manner. don't over do it or you are just ripping up roots for OCD behaviour.
This can definitely be useful once you develop some familiarity but there may be better ways to control the outcomes.
e.g. in soilless, 10% runoff ensures nutes don't build up. It may rest higher than the exact fertilizer formula, but it will reach an equilibrium that stays consistent, which is all that matters in a soilless context. if you also use a ph-buffered fertilizer, there's virtually nothing that can go wrong in all contexts but an act of god, lol.