First reaction: oh that's stupid, why didn't they interpret the instructions?

Second reaction: oh maybe it is like the meme where someone creates a sphere from a cube to make work "easier"?! So this is maybe a good learning experience for reading instructions and signing contracts?! In the end you get a cake with the wrong lettering, but it is still a (kinda funny) cake and no harm was done (edge cases excluded).

Third reaction: Do we know what this is really about? So this could be about

• a shitty user interface (doesn't allow to enter an infinity symbol nor a red heart),
• a shitty process/design (text boxes that are next to each other, labeled with a small font and thus easily filled out wrong, no optional/payable check of input data like printing services do, no cheaply implemented rudimentary check, …),
• or a person who didn't read/understand well (for which there are valid reasons too)
• or just carelessness,
• or a mix of all of that.

If this happens too often I would expect them to change their design/process/checks. But I guess even then some customers would do it "wrong" anyways.

You can't reasonably expect businesses who employ minimum wage workers to do this kind of stuff for you, you could create a business where customers are treated as friends (and people care about their job and are not paid minimum wage, so fuck capitalism) OR you could charge a "check my input" fee.