Connect calculation error

I have noticed that running a calculation, Connect takes account of the of the circuit current and not the fuse size as per your calculation help.

BS7671

It> In (divided by the grouping factors)

My circuit is protected by a 100A MCCB and has an 80A load.

It = 2-C SWA 4D4A ref E 128A.

The grouping factor of the SWA 2C cable is 0.78. 100A/0.78 = 128.2A grater than It, therefore the cable is under sized. 

When the load is fixed at 80A the circuit passes, when fixed at 100A the circuit fails. In both instance the circuit should fail. 

The calculation seems to take no account of the protective device size, and sizes the cable on the load only. Meaning that under normal operation should the 80A load increase to the protective device size of 100A the cable is not rated to take the load.

Regards

Stuart