See the attached screen capture showing the size of the .label-notification background is scaled based upon the content in this case digit(s). If the digit is one (1) digit then the background is a vertical oval. If the digit is two (2) digits the background is a circle. If the digit is three (3) digits the is a horizontal oval.
I would be beneficial for style consistency to set the background as fixed size based upon three (3)digits.
Todd