ABS has made two issues of additional shares since listing:
A 2:11 rights issue at $10.80 on 25 September 2002 and
A 5 for 1 split on 20 November 2002.
I suspect that you have not adjusted your chart for these, or your data vendor has missed them or done them incorrectly if you have a data vendor who makes adjustments for you.
I am going to deal with this issue in my upcoming Newsletter No 31.