One advice - make new SQL file (copy old one and erase everything inside)
Copy the first field of you'r "custom_npc" sql located in "sql" folder. Field should look like this one ..
INSERT INTO `custom_npc` VALUES ('99999', '31228', 'Roy the Cat', '1', 'Classes Trader', '1', 'Monster.cat_the_cat', '9.00', '16.00', '70', 'male', 'L2ClassMaster', '40', '3862', '1493', '11.85', '2.78', '40', '43', '30', '21', '20', '10', '490', '10', '1335', '470', '780', '382', '278', '0', '333', '0', '0', '0', '88', '132', null, '0', '0', '0', 'LAST_HIT');
after you copied it , just edit statistic and add you'r one from your npc :)