This system uses the player objects Y coordinates and the Y coordinates of the platform object.
The plry input is the constant player objects Y coordinate
The value input will be the height in pixels of the player object plus the platform object. In the example the platform is 2 pixels in height and the player is 15 pixels in height which makes 17, so the input would be 17 in this case. If however you have a character select system and the characters potentially have different heights the platform can be change depending on the character you have selected making it pretty universal.
If you have any problems or need help setting it up please ping me.