what is the change/difference of the platelet count of patient 42757 measured at 2102-11-07 05:01:00 compared to the value measured at 2102-11-07 00:15:00?
select ( select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 42757 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'platelet count' ) and labevents.charttime = '2102-11-07 05:01:00' ) - ( select labevents.valuenum from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 42757 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'platelet count' ) and labevents.charttime = '2102-11-07 00:15:00' )