CSS shorthand peoperties described as
selector {
font: font-style font-variant font-weight font-size/line-height font-family;
}
1) In your case: font: 400 14px "Helvetica Neue";
here you not defining any line height hence its taking default line height and Text seems to be vertically aligned top
2) if you use font: 400 14px/22px "Helvetica Neue";
here you are defining line height - 22px and this will be vertically middle aligned
Sidenote
vertical align middle works because height of LI = line height