Should I Be Concerned For The X Mark On The Mammogram Report?

had ultrasound on both breasts today. When it was over and tech left room, I could see two images on the screen showing dark spots. Would this have been my images? Why woudl she leave it on screen? Spent a lot of time on my left breast (clicking on keyboard etc)and I had been called back for a second mammogram (come impression) on left and ultrasound, They marked my left breast with an x on upper part of breast near where it joins chest. I am 46 and this is first mammogram/ultrsund in 15 years.