very sorry to hear about your refusal. Its hard to undersrtand why they reject sometimes.
they must have some valid reason, else they wouldnt simply reject, like a popular misconception here.
my guess is, an indian 3 yr diploma gives you entry to 2nd year of engineering course...may be thats why they took it as 1 year of education, FT at uni level. also, you can join the diploma after class 10 . YOu dont need to have 12 years of schooling to join diploma courses. may be thats why reduced points. for you points seem to have been calculated for 10 years of school + 3 years dploma = 15 points .
I am confused, when they say Diploma, they should atleast specify and compare it to some standard, for eg, a canadian diploma standard..
For Eg, in denmark immigration we8bsite they clearly specify how much points for indian/pakistani degrees, their equivalent etc
I hope your re-consideration letter to the program manager at CHC , works
all the best