Treatment of overflow of itc in construction service

Construction of a complex, building, civil structure or a part thereof, intended for sale to a buyer, wholly or partly. [The value of land is included in the amount charged from the service recipient] 12% With Full ITC but no refund of overflow of ITC. my query is what this line ''With Full ITC but no refund of overflow of ITC'' mean??? Suppose in July month : ITC available = 500000 GST liability= 400000 What about Balance ITC=100000 Whether it will be carried forward to august or not ?? or it will be carried forward but I cant claim its refund ?????