In my personal experience I’ve had various moments where the item count is different between devices. Questions about item count have been asked before on this forum several times. To me, the item count appears buggy, but it’s difficult the figure out why.
The most extensive description I’ve made about this issue can be found in the post below. That setup involved completely new installed software, but still one device reported one item less than the others. After deletion of that device (and resync) all databases were suddenly similar. @eboehnisch added it to his to-do list (see his reaction at the end), and in my recollection new DTTG releases did indeed address item count in the change log. But perhaps some root cause for item count discrepancies is still present?