Just add line-height: 17px;
to your CSS. Or whatever number is best for your needs
i.style-switcher-btn {
right: 0;
top: 60px;
color: #fff;
font-size: 18px;
cursor: pointer;
z-index: 555555;
position: fixed;
padding: 7px 19px;
background: #585f69;
border-radius: 6px 0 0 6px !important;
white-space: pre;
line-height: 17px;//ADD THIS
}