X marks the spot – a print job
MacOS Bash + OfficeJet Pro 8600, 46

(yes ''|sed $[$2*3/5]q;printf %$[$1*4/5]sX)|lp

Origin is the top-left corner.
I did a test print to check the character dimensions of what gets printed by lp to my printer - it appears to be 82w x 64h, so (integer) multiplying percentages by 3/5 and 4/5 respectively gets within the 10% tolerance.
Result, with command-line input of 25 75: