Nine and a half inches, gees I'd top it right off. For one plant under a 400 watt you'll want to veg for a while to get a decent yield/return on investment. Inidicas like to reach maturity before they flower. This occurs when the branches alternate from side to side. Usually for seed it's six weeks, clones may go quicker. You'll want 12"-18" over the plant to the light, if it's an uncooled reflector. You will LST the plant to keep it in your limited area. Are you growing in soil?