EF is showing the following

1. Only 2 F seats available
2. Only 19 J seats
3. 96 seats in Y

You should use this as a guide only. There may be plenty of Y passengers who are booked on the flight but they haven't been allocated a seat yet (there's still a lot of people who aren't Skywards members). That 96 could be a lot less.

J could be the same - although not as bad. The system says its prepared to sell 4 seats in J or C or I.

And I would think F would be an accurate indicator.

You'll find that at around the 6hr mark, you'll see a lot of seats in Y disappear as the systems starts to allocate seating. If it doesn't move a great deal you'll know that the flight isn't that full.

Sometimes a friendly EK staffer might tell you the load. I always call SIN and they tell me (within limits).