The Assembly Grid is the group of colored rectangles on the left side of the screen when you're in the Assembly Module.
Each rectangle represent an individual location. If the rectangle is grey it's empty.
The green to red color spectrum indicates that there are item(s) on the location. The color is relative to the production due date.
Red indicates a Late or Rush order
Orange indicates an order due within 12 hours
Yellow indicates an order due within 24 hours
Greenish-Yellow indicates an order due within 48 hours
Green indicates an order due in more than 48 hours
If the rectangle is black it's your current location. If you're using a conveyor that means the conveyor is spinning relative to that location. If you're using an assembly bay then your current location is just the location you last assembled to.
You can click on a location to open the corresponding order, or hover over a rectangle to see the due date.
There are 3 numbers at the top of the grid, above the name of the Assembly station. Items is the number of items assemble at the current station for the day. Bags is the number of tickets that have finished at the station for the day. Todo is the number of items left to do for the day.