So what part of 15-21 Feb can be considered as 'sales'?
All the ~160 games are on sale Feb 8-21. They are discounted from regular price (eg. 30% off for non-members, 40% off for PS+ members). In part 1 (Feb 8-14), you can use coupon for another 15%. In part 2 (Feb 15-21), no more coupon, but the sale prices still apply.
For example, if a game is S$100. If non-member gets 30% off, the discounted price is $70. PS+ members get additional 10% off (applied to the
regular price, so 30+10=40% off), the discounted price is $60. If use coupon, that's another 15% off (applied to the
discounted price), so non-member $59.50, PS+ member $51. In part 2, no more coupon, so $70 and $60 respectively (still considered sale, cos regular price is $100).
Simply put,
if want to buy, do it by today and use the coupon (assuming you haven't used it yet). Also, if the regular price of the item(s) you are buying is >$69 and there is additional 10% PS+ discount, if you are not PS+ member, go buy a 1 month PS+ at $6.90 first, then buy the item(s).