what was the last value of patient 12775's magnesium laboratory test since 11 months ago?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 12775 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'magnesium' ) and datetime(labevents.charttime) >= datetime(current_time,'-11 month') order by labevents.charttime desc limit 1