If you mean the number in the bottom right corner of the PokerTracker 4 window that's visible from every section (Community, Play Poker & View Stats) then that's just the number of hands imported while playing and it will not change when using filters. If you are referring to something else then in 'View Stats' there are multiple sections (Results, Statistics, My Reports, & Graphs) and within each of those are multiple different reports so which report are you currently using? Bear in mind that if you have a session that crosses over midnight but have not configured the 'My Day Starts At' setting in 'Configure > Reporting Options' to a time you don't play then that can affect things depending on the report you are using when filtering by day. If necessary please attach
screenshots of your PokerTracker 4 report window with each filter either here or privately in a
Support Ticket so we can see what you are referring to.