Create a copy and edit SambaSettings.txt as show here.
Try increasing font-size setting to a bigger value.
Don’t forget to backup SambaSettings.txt before editing and be sure your printer type is configured as HTML.
V3’s HTML printer is limited compared to V4 or V5. For example it don’t support bitmap printing.
You can ask further V3 questions on sambapos.org website. V3 questions asked here leads to a lot of confusion.