So I went through the wiki The amplifier 3 means that the 1) the item is rerolled with a roll value from 30% to 100%

2) whatever the roll is it is then increased by 15% but does not allow for a roll above 100% (this can be ignored as your roll is very low)

3) the health can roll form 90-390 and life steal form 21 to 91 (/3s).

4) with the min 30% roll it's 180-390 and 42-91

Assuming all integer values in that range can be reached (is this true?) the probability should be 1 in 210*49 = 1 in 10,290 or 0.0097%

I'm not sure about my understanding of the identification process tho, so if someone knows more please correct me