How should tall boots fit?

I bought a pair of field boots and they're really nice and comfortable. But they're breaking in and I'm worrying that they're going to be too short. I've ridden in them for about a week and they have dropped, but if they drop anymore I think they'll be too short.

My calf length measured to be about 17 inches and the boot height is 19 inches. They now fall just below where my knee bends. If they drop anymore I think they'll just be too short. They have a Spanish cut, so they look taller, but I don't want ill fitting boots to ruin my riding. They also have zippers if that makes a difference.

I really want to know how boots should fit after they have broken in. I want to know if I should just keep these boots for longer or get a new pair.

Here is the type of boots they are.

Footwear

all I know is when I got my ariat tall boots the lady fitting them said they would fit perfect after they dropped and folded correctly.

When I first tried them on they DUG in the back of my knee too high about an inch or so (which she said told her they were going to be a perfect fit!) I believe she told me that they should still be up at the level where the back of your knee bends after folding/dropping.

Any more and they're too short.

Ok thanks. Mine are right below where my knee bends

Can anyone else help?
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Pictures might help.

Here's some pics.

This is only the 2nd time I wore them in these pictures.

Even if they drop 1/4 - 1/2 inch I still think they will look ok because of the spanish cut top.