RE: GST ITC's on my self employment home office expenses? My office is 10% of home sq.ft. do I claim 10% GST ITC's on hm expenses? 90% GST ITC's amount goes where then?

Can I include the 90% unclaimed GST amounts back onto my home expense totals? Or does that amount just become unclaimed?  Can I claim all the GST on Auto fuel receipts (eventhough I only drove for business 66% of total KM's on my vehicle?) So the remaining GST ITC amounts become unclaimable? or could they be rolled back into an expense somehow?