Currently I'm staying at Farrer Park, looking places nearby would be nice. Not sharing room with anyone. May I know where is your location?

They don't have a cut-off date for these kind of things.

eg:
Entered 3/1, exit 21/1 (19 days)
Entered 1/2, exit 25/2 (25 days) = 44 days total
Entered 1/3, MUST exit 16/3 (16 days) = total 60 days

Your next re-entry will be on 3/4 because 3/1 - 3/4 is 90 days (assuming Feb has 28 days)

Assuming you didn't re-enter on 3/4, but re-enter on 10/4 instead, you must exit by 28/4 as you've used up 60 days.
Counting the re-entry date on 1/2, you have cumulated yet another 60 out of 90 days stay.

If you literally want a fresh 60 days, ensure you did not enter SG for 90 continuous days.

This is sort of like compounding days, some guys from Agencies who liaise with MOM taught me this calculation. Similar to the demerit points on Malaysian Driver's License.

Its easier to explain this by simply drawing a  few lines then using words. Hope you get the picture.

p/s: This is not info from Custom or anything, just some people who liaise with MOM, even they might be wrong or info has been updated etc.
But easiest and surest way of em all, ask the officer who is stamping for you, if you are shy, go find does who are on guard/patrol duty, ask politely and most people will be more then happy to help.