If your Star mC-Print 2/3 printer prints light text on receipts, you can adjust the print density as follows:

Download "mC-Print Utility" app.

Select your printer. Then go to Printer Settings.
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Now go to Memory Switch Settings.
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Find Print Density and adjust it (+3 for the darkest print). Click Apply.

To change print width, select Printable Area here and adjust accordingly.
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Proceed with a test print.