The reason for seven, yes some people Will disagree and say wait for the other appliances
A few examples
House fire
4 in BA, 1 IOC, 1 Pump operator, 1 person getting water in = 7
Grass Fire 1 Line
1 IOC, 1 Pump operator, 5 on one Line ( 90m is a lot of hose to get working with in some areas)
If you went to a job like Mt Osmond 1 line with a crew of seven was still hard work on a day like that, the more the better, it must be safer less work than six
Grass Fire 2 Lines
1 IOC, 1 Pump operator, 3 on one line and 2 on the other.