###HUMAN: how much different is patient 016-8658's weight last measured on the first hospital visit compared to the value first measured on the first hospital visit?, ###ASSISTANT: SELECT (SELECT patient.admissionweight FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '016-8658' AND NOT patient.hospitaldischargetime IS NULL ORDER BY patient.hospitaladmittime LIMIT 1) AND NOT patient.admissionweight IS NULL ORDER BY patient.unitadmittime DESC LIMIT 1) - (SELECT patient.admissionweight FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '016-8658' AND NOT patient.hospitaldischargetime IS NULL ORDER BY patient.hospitaladmittime LIMIT 1) AND NOT patient.admissionweight IS NULL ORDER BY patient.unitadmittime LIMIT 1)