How to get values from UI designer fields to Process Variables?

Hi, 

So i have a problem my workflow should star after 10AM, so i have a start timer with a daily condition after 10AM.
Then i have a task "Check inventory" (this is supose to be a person checking inventory and then he should be able to say if another products are needed or not, to make a request) 
I tried making a BDM with a boolean that means if i need more products or not, and a text variable to especify the products i need

In the execution tab (pool selected) i created a contract (add from data) and selected inventoryInput and the two variables from that BDM

But my timer gets an error says "An instantiation contract cannot be used with this start event type. Use the none Start Event" and i don't understand why is this? usually i do BPM like this to get UI designer values, but now i'm stuck, I'm pretty new to Bonita and BPM.

 

Please try below way

1. Create the process variable instead of BDM Variable

2. Get the UI variable as part of Contract

3. Assign Contract Variable to the Process Variable

4. Use the Process variable for further business logic implementation.

 

Thanks