Double Horizontal Lines as Guides

Hi,

I recently began using CS6. It's been quite a while since I used CS3, so maybe this was an anomoly there, too.

My question is this... Why does InDesign show double horizontal lines on the display for guides?

The vertical guides are displayed as single lines. All horizontal guides are displayed as double lines. If I zoom in, the lines stay the same distance apart on the display, which indicates theres a single line, not actually two guides.

Is this feature of InDesign?

Thanks

Jeff