partial block that experience

As follows: to create in the box density is partial blk 30, and 30 is the density of up to 30%
(see description before the Internet say 1-30% = 70%, but based on my own operation found 30 set out to do the results clearly be lower than the density of 70)
createPlaceBlockage -type partial -density 30 -Box X1 X2 Y1 Y2
createPlaceBlockage -type partial -density 70 -Box X1 X2 Y1 Y2