\$pV/\sqrt {Hz}\$ in Power Spectral Density
A 62 ohm resistor produces 1 nanoVolt of noise in 1 Hertz bandwidth.

A 6.2 ohm resistor produces 1nV/sqrt(10) = 1nV/3.16 = 0.312 nV

or

312 picoVolt noise in 1 Hertz bandwidth.

The noise power increases linearly with bandwidth. As "Andy aka" explained, the noise voltage increases with the squareroot of bandwidth, hence the dimensions you are seeing.