I tried to make clear explanations of some passages in this formula on the right side of the equations, but there's always something that goes wrong (I mean that I don't aesthetically like the result). Can you help me?

This is my latest try:

```
\documentclass{article}
\usepackage{amsmath}
\usepackage[margin=1.5in]{geometry}
\begin{document}
\begin{equation}
    \begin{aligned}
    \eta &=\frac{W}{F(\rho_M)-F(\rho_M')}=\frac{W}{F(\rho_M)-F(\rho_S')-F(\rho_A')}=  &\textrm{\parbox{8em}{from point 4. of the list above,}} \\
     &=\frac{F(\rho_W')-F(\rho_W)}{F(\rho_M)+F(\rho_S')+F(\rho_W')-F(\gamma_{SW},H')-F(\rho_S')}=  &\textrm{\parbox{8em}{from the equality  between point 3. and 4.,}}\\
     &=\frac{F(\rho_W')}{F(\rho_W')-F(\gamma_{SW},H')}= & \textrm{\parbox{8em}{from point 1.  $F(\rho_M)=F(\rho_W)=0$,}}\\
     &=\frac{1}{1-\frac{F(\gamma_{SW},H')}{F(\rho_W')}}  & \textrm{\parbox{8em} {obtained by dividing numerator  and denominator by $F(\rho_W')$.}}
    \end{aligned}
\end{equation}
\end{document}

```

[![Enter image description here](https://i.stack.imgur.com/ZIVGL.jpg)](https://i.stack.imgur.com/ZIVGL.jpg)