instruction: what was the first time patient 28959 had the maximum platelet count value until 06/2103?
response: SELECT labevents.charttime FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 28959) AND labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'platelet count') AND STRFTIME('%y-%m', labevents.charttime) <= '2103-06' ORDER BY labevents.valuenum DESC, labevents.charttime LIMIT 1