My manuscript went from "With the Editor" to "Decision in Process" after I submitted it to a journal, which had a median decision time of 10 days. After 18 days the status changed to "Decision in Process". What might this imply? If it was intended to be rejected within the 10-day period, shouldn't they do so? Why is there a status change after eighteen days?
If the median is 10 days, that means that half of decisions take longer than that.
Plus, among the half of decisions that get taken in 10 days or less are presumably all the desk rejections that happen within two days. So conditional on not being desk rejected, median time to decision may be a lot higher.
Finally, time to decision is a discrete variable with support on the nonnegative axis. Such distributions usually have a mean (much) larger than the median.
Bottom line: the elapsed time, in itself, is no cause for concern. 18 days is actually easily a case of "the editor in chief got a case of COVID, couldn't work for a week, and is now slowly digging through their accumulated work". I would not yet start contacting anyone.