Using the rules for significant figures, what do you get when you subtract 15.54 from 508.9538?

According to the rules for significant figures, simple decimal subtraction is done. But since 15.54 is only accurate to the hundredths place, then the resulting difference should also be rounded off to the nearest hundredths. This is shown below:

508.9538 - 15.54 = 493.4138

Rounding off to the nearest hundredths:

= 493.41