Hi Gabriel, nice to meet you and welcome to the forums!
TOEs come in all shapes and sizes, the Soviet TOEs did suffer a lot of variation on their paper strength along time. Also, the realities of life mandate that paper strength has little or nothing to do with the actual field strength, which varies day-bay-day, even hour-by-hour.
If I can offer my humble opinion, and sice your trrop ratio (15:1) is rather a coarse one, for those divisional subunits I wouldn't be too fussy and follow a number that I feel is right.
So if your Battalion has 3 batteries of say 6 guns, does it really matter much if you display 1/15 of 18 guns or 1/15 of 12 guns? The difference doesn't ammount to much, does it? I already have trouble with 1:5 at my micro-armour scale, let alone at 1:15
And where are your photos?
Oh, the Red Army did not use much in the way of tactical markings, numbering etc, all those are very rare and short-lived. There was no developed sign system like the British or German one, only some number apllication here and there, generally. Take a good look at photos.
The Russian Battlefield - Camouflage of the Soviet Tanks