Figures on the Territorial States (minus the RWR):
Magistry:
2750: 1 Division (9 regiments)
2765: 20 Divisions (77 conventional regiments, 108 BattleMech regiments) (will be joined by ~45 Reg'ts of irregulars)
2770: ~20 Regiments
Loss ratio: SLDF: 391 regiments; Magistry: ~210 regiments
Outworlds:
2750: 5 Regiments
2765: 19 Divisions (72 conventional regiments, 100 BattleMech regiments) (will be joined by ~30 Reg'ts of irregulars)
2770: ~22 Regiments
Loss ratio: SLDF: 445 regiments; Outworlds: ~180 regiments
1255
Concordat:
2750: 13 Regiments
2765: 21 Divisions (78 conventional regiments, 115 BattleMech regiments) (will be joined by ~40 Reg'ts of irregulars)
2770: ~33 Regiments
Loss ratio: SLDF: 419 regiments; Concordat: ~200 regiments
The 2765 totals include the "Secret Army" divisions funded/trained by Amaris -- but note, there are ~60 of these, rather than the ~50 claimed in the text (the figures above come from pgs 50, 94, 95 and 97; size of the Secret Army discussed pg 51). Maybe the Territorial States had time to build up their armies on their own; we know the Magistry did (or, at least, was able to hire mercenaries), but the other Periphery states are specifically stated (pg 51) to not have been able to do the sleight-of-hand which allowed the RWA to have such massive contingents of reservists, which suggests the expansions of the Periphery State militaries between 2750 and 2765 are unlikely to account for the "missing" 10 divisions.
Periphery Divisions seem based on 9 regiments/division, while SLDF Divisions are based on 12 regiments (4 brigades) per division (plus supporting units). Periphery regiment totals seem far too BattleMech-heavy for thrown-together forces, and the description of the Secret Army divisions on pg 51 indicates that these forces should not have been 60:40 BattleMech (even the SLDF is described as having only slightly more than half its regiments being BattleMech formations).
Traditional descriptions of SLDF Divisions are also predicated on the 9 regiment (3 brigade) structure, but this is overturned on page 36 of H:LoT I, where it states that all SLDF divisions have a brigade of pure armor, in addition to the three other brigades, one of which is always 'Mech, one always Infantry, and the third one or the other. So SLDF Divisions should total 12 Line regiments + support troops, but this is not accounted for in the statistics on SLDF losses on pages 94, 95 and 97. Adding 3x more regiments per Division destroyed/disbanded revises the total SLDF losses to:
Magistry: 511 regiments
Outworlds: 586 regiments
Concordat: 554 regiments
And this moves the comparative loss ratios from ~2:1 (1255 to 590) to ~2.8:1 (1651 to 590).