Can a 4 mm mole be very serious?

hi i had a mole removed 2 days ago. it was pretty much flat, kind of like a beauty mark. they had to "punch it" out as they call it which is basically cut it out and stitched it back up. i was just curious if you guys think its serious. i know i'll find out in a week or so but i'd like to have opinions. it was measured at just under 4 mm. it looked perfectly circular. the reason whys she took it out was because she said it had a bad nature to it and look kind of pigmented under the magnifying scope but not to the naked eye. i read online melanoma is usually bigger than 6 mm but i was just curious. please and thank you!