What's the minimum distance between the two fire-stopping arrangements?

Question:

Where BNO Residential Sub-mains exit a riser, run along the common area corridor and then enter an apartment, the cable would pass through fire-stopping insulation where it leaves the riser and again where it enters the apartment.

One particular fire-stopping manufacturers approved fire-stopping solution involves taking each cable through the fire-stopping wrapped in a 300mm length of 30mm thick rockwall type pipe insulation giving an insulation make up of 80mm long of 30mm rockwall wrap, followed by 140mm long wall opening of 30mm rockwall wrap plus 150mm all round of rockwall batt with intumescent spray over, and 80mm long of 30mm rockwall wrap on the other side of the wall.

From the regulations If you interpolate the 200mm & 400mm insulation correction factors you get a correction factor of 0.57 for a single instance.

Do you need to apply and interpolate the correction factors twice giving you a correction factor of 0.45 for effectively a 600mm length of cable through insulation or can can you ignore the 2nd instance if it is over a set distance from the 1st instance with sufficient length between for the cable to cool down?

If able to ignore the 2nd instance what would be the minimum distance between the two fire-stopping arrangements.

If you have an opinion please add it in the comments below...