Unrealized chart "cost" column- including dividend discounting?

I'm probably too oblivious (and certainly too ignorant) for my own good- but it seems to me this cost column is getting lower for some older shares I bought- as if deducting the dividends I've earned since purchase.

So is it?

Dearmad,

Yes the cost basis tool we have takes into account corporate actions including potentially some dividends depending how they are classified. If you want to review your specific account or the cost basis of something in there please call us 877-495-5464.

thanks,
Dave