It may be a glitch of some sort. All sp you get from selling stuff from your shop goes to your till.

Your shop log won't show you only the most recent sales, it shows you everything you've ever sold.. and if you sell say, one of an item at once point, collect the sp, and another one sells then it'll show on your shop log as 2 having sold, condensed.

I hope that makes some sense?

If you haven't done so already please file a ticket for this.