I caught two guys at work glancing at my cleavage, why?

I was sat in my bosses office, I was wearing a dress which stops below my knees and the cleavage comes up to where my actual cleavage line begins so it's not on show (if that makes sense).

You could see the shape of my boobs, maybe that's why the kept glancing, but I was talking to them so they knew I was looking at them so why would they glance down?

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+1 y
It wasn't just one glance, it was multiple
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+1 y
These guys were a lot older than me, in their 40s, and it wasn't just one glance, I saw multiple and that's when I was talking to them.
I caught two guys at work glancing at my cleavage, why?
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