Minecraft wiki entry for forceload, associated text: Forced chunks get load ticket with load level of 31, the same as ticket chunks get by being in player's chunk loading distance, which means that the said chunk processes all aspects of the game while adjacent chunks get activated by the load level's spread but since it increases its load level each time, adjacent chunks don't process every aspect of the game as well. See also chunk.
Crops do not grow in forceloaded chunks unless a player is nearby. Crop growing (without the use of bonemeal) depends on chunk ticks.
Coordinates are actually block coordinates. In order to forceload chunks 0,0 to 1,2, the player should use /forceload add 0 0 31 47, which loads chunks 0,0 to 1,2 (1,2 inclusive, 2×3 chunks).
When using /forceload add 0 0 10 30 chunks 0,0 to 0,1 are actually loaded (one chunk equals 16×16 blocks on x/z axis). However, /forceload query gives result in chunk coordinates.