I just noticed when we are in strong trend day the balance of orders tends to get firmer than usual. And when we get in a range, order’s size balance gets wider:

This is important because the z-value suppose to tell when the market  is getting trendy, but I just noticed it is a lagging indicator. Look in the minute chart (left chart), the chart line between z-value and price plots the difference between bids minus asks orders, meaning if >0 then it the ammount of bids trying to get filled at that moment, if negative then you are seeing how many contracts are offered in the ask side.

Check the long term chart (30 mins, right side) how volume increased when bid-ask size balance narrowed and very much the same in the opposite logic, wider bidask sizes while volume getting lower.

In the mean time z-value only confirmed the trend concluding the dabate.