Potency and quantity calculation in sales order details line P4210 ?

Dear Community,

I have setup item A with a standard potency = 33.333

potency applies on unit of measure "TP" (special handling)

I have also a uom conversion, 1 KG = 10 TP

so in conclusion, 10 TP = 1 KG x potency = 3,33 KG

it works well in item availability screen, problem is with the P4210

case 1

item A, primary qty = 300 uom TP

system populates the values : secondary qty = 300 TP ; total weight = 100 KG --> the math is good

case 2

I key the item A, primary qty = 100, uom KG

system populates the values : secondary qty = 1000 TP ; total weight = 100 KG --> the math is wrong, I m expecting secondary quantity = 300 TP