With a massive 1400 scouts the 10th Host should gain in the vicinity of 1200+ new marines (potentially 60 per company) when the growth/training period is up.

With the new forge-capacity there should be enough wargear for all by the time.

Net gain of marines depends on the amount of action throughout the period. Looking back at the last cycle Castor was conservative and careful, but also conducted several large operations that gave him resources (not least in terms of a vast fleet). The Warleader is operating with a projected attrition rate of 6-12%, depending on circumstances. His best aestimate is that there will be a 900 marine net gain, or about 45 per company, bringing average companies up to about 170 marines.