Help With Picture Puzzle Please .......

[Gizmonster]

Got to level 16 on this picture puzzle thingy and this one has me stumped:

http://i264.photobucket.com/albums/ii200/Burnleymoonbeam/Funky%20corners1_zpsbllxa82u.png

I can alter each of the 4 digits, so I suppose each symbol above each digit, somehow represents a number. When I get the 4 digit number correct, it will let me know, so I can progress to the next level.
Anyone any idea what 4 digit number I need - plus a bit of an explanation so I can slap myself on the head and shout, "D'oh" ........

If you want to tackle the whole puzzle yourself:

http://www.coolmath-games.com/0-clickplay-time

[Gizmonster]

By the way, the level title is meant to be a clue, so "funky corners" .... errmm okay, what does that mean lol ??

[Mamyalynne]

I'd try

4132

To make them into squares.

Guess.

[Gizmonster]

Just tried that - didn't work :(

[Mamyalynne]

Hmmm, rethink

[Gizmonster]

Solved now.

You wouldn't have got it unless you played the game, as the corners of the perforated paper all turn over if you click on them and you then need to input the corresponding corner, relating to the symbol.