I have a text list with the following structure:

  292G.- La Ilíada ; Collection one (volume 57) ; Homer ; http://www.ataun.eus/BIBLIOTECAGRATUITA/Cl%C3%A1sicos%20en%20Espa%C3%B1ol/Homero/Iliada.pdf
  - I have to download more ancient greek texts.
  - Another note line.

  293G.- El Quijote ; Collection one (volume 32) ; Miguel de Cervantes ; http://www.daemcopiapo.cl/Biblioteca/Archivos/7_6253.pdf
 - Masterpiece.

  294G.- Crimen y castigo ; Collection one (volume 2) ; Fiódor Dostoyevski ; http://www.ataun.eus/BIBLIOTECAGRATUITA/Cl%C3%A1sicos%20en%20Espa%C3%B1ol/Fedor%20Dostoiewski/Crimen%20y%20castigo.pdf
  - Russian masterpiece.

Starting at 292G, I have 100 volumes of a collection disordered (in the position 293G I have volume 32, in 294G volume 2, and so on). I wanted those 100 volumes sorted by the volume number (which can be found in the second field), so the primary number (the number with the G) has to be recalculated.

The expected output is:

  292G.- Whatever title ; Collection one (volume 1) ; Whatever author ; whatever link for donwload
  - Notes here if there are.

  293G.-  Crimen y castigo ; Collection one (volume 2) ; Fiódor Dostoyevski ; http://www.ataun.eus/BIBLIOTECAGRATUITA/Cl%C3%A1sicos%20en%20Espa%C3%B1ol/Fedor%20Dostoiewski/Crimen%20y%20castigo.pdf
  - Russian masterpiece.

etc.

I suppose sort has the answer here, but this is beyond my rookie skills.