Subtotal not so good

Hi,

Subtotal is calculate like :
Total - VAT = Subtotal

But in real life :
Subtotal = Subtotal group + Subtotal group…

We have a little différence if you have amout.
exemple :

see in attachement …
But for me is :
1110 + 407,14 + (400*6,40) = 4077,14

Can you help me please ?
Chris