Calculate the overall gearbox size $($roughly$)$ based on the already known number of teeth of each gears and the catalog data from the gear manufacturer?

Please explain what we are trying to do$,$ how to use this data that we collected, particularly how we get $40$mm and $130$mm in the photos what do they mean?

Brief introduction of the question:

A reverted gear train is needed to provide a speed increase output, and need $2$ pair of gears. The number of teeth of each gear is found as follows and the data of each gear is found from the munufacturer's catalog.

Figure $2$ Gear $1$

Figure $3$ Gear $2$

Figure $4$ Gear $3$

Figure $5$ Gear $4\backslash$table$[[$Gear$,\backslash$table$[[$Module$],[($mm$)]],\backslash$table$[[$Catalog$],[$Number$]],\backslash$table$[[$Number$],[$of$],[$Teeth$]],$Material,$\backslash$table$[[$Pitch$],[$Diameter$],[($mm$)]],\backslash$table$[[$Bore$],[$Diameter$],[($mm$)]],\backslash$table$[[$Hub$],[$Diameter$],[($mm$)]]],[1,4,$SS$4-65,65,$S$45$C$,260,30,56],[2,4,$SS$4-25,25,$S$45$C$,100,20,60],[3,4,$SS$4-54,54,$S$45$C$,216,30,56],[4,4,$SS$4-36,36,$S$45$C$,144,22,56]]$

Table $1$ Dimension of selected gears

Figure $6$ Countershaft Rough Draft with Gears, Bearings, and Shaft Gear $2$

Figure $7$Countershaft's FBD