Use the ROUTING OUT BATCHING button to split the Work Item up into a number of individual Work Items (the number being different from the input number).
As a special case, a batch may start in your simulation as one batch and be immediately split into a number of individual Work Items.
This controls the number of items that arrive at one time. If an “arrival” occurs at time 10:30 and the number of items set to leave the Start Point is “Fixed” 20, then 20 items of the specified Work Item type will arrive at 10:30.
The number of items in a batch can be determined by a distribution. They can also read global variables. Hit the more button, highlighted in red in the image, or put the cursor in the edit box and hold down shift while you double click. Both of these will open the formula editor where you can enter any expression you like.