Hello, I just tested this: By default the value is 1rem. If you want to enlarge => x1.2
You can add the following rules in custom style.

.bx-def-unit-alert {
min-width: 1.2rem;
height: 1.2rem;
line-height: 1.2rem;
border-radius: 1.2rem;
font-size: 1.2rem;
}

However, do not be too big because you are also blowing other bubbles.