You can use the IN clause for this, which is easier to read (and possibly more efficient?) than building a giant OR list. Try something like:
IN
OR
UPDATE ibf_membersSET points = points + 500WHERE mgroup = 15AND id IN (5, 7, 10, 11, 16, 25);
Just add another condition to your WHERE clause:
UPDATE ibf_members SET points = points + 500 WHERE mgroup = 15 AND id IN (5, 7, 10, 11, 16, 25)