What version of SAS and SAS/Stat are you using?
If 9.4, SAS/STAT 14.1 this functionality is now in PROC LIFETEST and you can modify your graph template.
Otherwise, I think the macro definition is here, and since it's SGPLOT you can modify it.
Take a look at the SGPLOT code and test it out.
https://support.sas.com/kb/45/addl/fusion_45997_13_fusion_45997_12_cif.txt