what was the last platelet count in patient 10624 since 03/2105?
select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 10624 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'platelet count' ) and strftime('%y-%m',labevents.charttime) >= '2105-03' order by labevents.charttime desc limit 1