plot 'plotfile.txt' using 1:($2+1) with steps title 'a0', \
'plotfile.txt' using 1:($3+2) with steps title 'a1', \
'plotfile.txt' using 1:($4+3) with steps title 'a6', \
'plotfile.txt' using 1:($5+4) with steps title 'a7', \
'plotfile.txt' using 1:($6+5) with steps title 'd0', \
'plotfile.txt' using 1:($7+6) with steps title 'd1', \
'plotfile.txt' using 1:($8+7) with steps title 'd2', \
'plotfile.txt' using 1:($9+8) with steps title 'd3', \
'plotfile.txt' using 1:($10+9) with steps title 'd4', \
'plotfile.txt' using 1:($11+10) with steps title 'ss'