I found a logical coherence between the values in table
if value is 000, partial product is 0
if value is 001 partial product is Y
if value is 010 partial product is Y
So similarly if value is 101, value is -Y, we can think of leftmost bit as sign bit and when it's 1, we complement rest of bits and check their partial product
like for 101, MSB is 1, so I do complement I get 010 and its PP is Y, so for value 101 PP is -Y.
and similarly for 111, on complementing we get 000, for which PP is 0, so for 111 PP is 0.