Good Day @Delano,
What you can do is add a Decision Point before each of the Processors, and connect it to the respective ExitTransfer (connected to the Processor).

In the Source, create an On Creation Trigger (Data > Set Label and Color), with the following logic.

current.stats.output.value % 7 < 3 ? 1 : 2
is the ternary operatior of (same as):
if(current.stats.output.value % 7 < 3) {
return 1;
} else {
return 2;
}
The first three items created in Source will have a label "Type" of value 1, and the next four items will have a label "Type" of value 2.

For the 3 Decision Points, create an On Arrival Trigger (Send Item), and leave the first Decision Point's logic as default.
Change the Condition in Send Item logic for the other 2 Decision Points as follows:
Decision Point near Processor B1:
item.Type == 1
Decision Point near Processor B2:
item.Type == 2
This ensures that for every 7 items created, the first 3 items (Type 1) will go to Processor B1, and the next 4 items (Type 2) will go to Processor B2.
Hope this helps.