When The Measuring Cup Measures Wrong

I noticed the first time I used my latest bottle of mouthwash (it's generic, from Target) a couple months ago.  I am supposed to use ten milliliters of it every time.  You, conveniently, get to use the bottlecap as the cup into which you pour the mouthwash because it has a little line that marks 10 mL.

But not this one.  Oh, no.  I open up the bottle, turn over the cap and pour ... but then I stop because I see that the line/notch doesn't measure 10 mL.  It measures 15.  I checked the instructions to make sure they didn't change because the changed the formula of the mouthwash or something.  Nope; you're still supposed to pour out only ten milliliters.  So I've been eyeballing my pours ever since.  But how can you tell if you're measuring exactly two-thirds of the only sure measurement you see in the cup/cap?

More importantly, how in the hell does this happen?  How does a company/warehouse/manufacturer use a cap that has a measuring notch that does not match the recommended amount of liquid that cap is being used for?  Is it a supply chain issue?  Does it have anything to do with the pandemic?  Or did they just flat-out screw up?  I can't believe it's a case of them saying, "Oh, well, we have these caps that totally fit with this bottle, but it has a measuring line that is five milliliters more than the recommended dose on the instructions ... eh, whatever, use those, we need to get rid of them.  People can deal."

The instructions also have a customer service phone number.  I might call it and ask what's up.