Ph of Organic Miracle Grow?

i decided to go very basic for the first grow, that is why i'm using the OMGS. no added anything, unless it's needed at some point.

my book specifies this: NOTE: because the miracle grow soil used in this book has a ph of 5.1, the water used to grow this plant was adjusted accordingly. watering done in the first half of the plants life was adjusted to a ph of 7.4.

so...i have two questions.

firstly, i'm wondering if the ph of organic miracle grow is the same as the standard miracle grow? i have a ph test kit and am wondering what i should adjust the water to that i'll be giving the soil and plant? is the organic still 5.1 ph?

second, i'm sort of confused why he says the ph is adjusted for only the first half of the plants life. if it's the same soil throughout the entire grow, shouldn't the ph continually be adjusted?

thx for your help

bump......

checking the runoff, yeah good idea. that makes sense.

my book says, ideally, you'll want 6.2 - 6.3 ph for soil grows. i've heard that miracle grow is pretty acidic, so i'll probably be adjusting the ph of the water upwards. but i'm not too sure, because i'm using organic and not just typical miracle grow. but it shouldn't matter anyways, as i'll know once i check the ph of the runoff..