I need help on discount code for supplier purchasing.

For the supplier, when I buy from them I get certain discounts,

e.g.

On standard line items, if my total purchases (calculated at retail price) is under 20000 I get 35% and if it is over I get 40%
For items on special, if my total purchases (calculated at retail price) is under 20000 I get 32% and if it is over I get 42%

I have set up 2 purchase discount bands, one called STD and I called SPC
For STD, I have assigned band 1 as 35 and band 2 as 40.
For SPC, I have assigned band 1 as 32 and band 2 as 42.
For items where I do not get discount or make a profit, I have not included and discount codes.

According to the help file "Purchase Discount Code Details", so far I am correct.

These STD and SPC I have assigned to the relevant stock items.
The relevant supplier has been set as default supplier ( I have not specified and code here but I've checked if I do set a discount code it defaults to band 1 being selected).

Now it refers to "Each supplier has a one digit Purchase Discount code, the value of this determines which discount band is used in calculating your cost price".

Now my questions are:

Where do I find the The one digit Purchase Discount code for the supplier. (I see that customers have a "Sales Discount/Markup Band", I assume the supplier should have something similar like a "Purchase Discount/Markdown Band".)
On the Stock Items details, I've configured the "Purchase Discount" on the Details-Purchasing tab. Is there anything I need to do with the supplier on the "Suppliers" tab.