The Conveyor Turntable distributes materials evenly up to 4 Conveyors assuming there is free space on the belt. If space is not available it will attempt to distribute to the next available belt.

NOTE: The Conveyor Turntable works best when it’s allowed to place material onto adjacent belts. Attempting to place directly into Hoppers can cause conveyors to get stuck.

To make a turntable split items to go to each direction evenly you need to meet a few requirements:

1) You must feed the turntable a item at least every 15 seconds or it will auto-rotate to try to find new input, messing up the balance of the split. You can feed it a batch of items then pause if you want, but if you do that you need to ensure that the size of the batch is a multiple of the number of outputs you are using.
2) None of the outputs can be full. They all have to be able to take their output when it is their turn.

Your turntable will pause for 15 seconds until it auto-rotates if the output ever ends up pointing at the input. To avoid this you need to feed it from the top or the bottom.