What points should be considered during the addition and subtraction of numbers with significant figures?

(N/A) In addition and subtraction of numbers with significant figures,the following points should be followed:
$(1)$ If the numbers are whole numbers,they should be added or subtracted using normal arithmetic rules.
For example,
If $A = 25 \text{ g}$ and $B = 2 \text{ g}$,then:
$A + B = 25 + 2 = 27 \text{ g}$
$A - B = 25 - 2 = 23 \text{ g}$
$(2)$ In addition or subtraction,the final result should retain as many decimal places as there are in the number with the least number of decimal places.
For example,add $436.32 \text{ g}$,$227.2 \text{ g}$,and $0.301 \text{ g}$.
$436.32 \text{ g} + 227.2 \text{ g} + 0.301 \text{ g} = 663.821 \text{ g}$
In the number $227.2$,there is only one digit after the decimal point; hence,the result should also have only one digit after the decimal point.
Therefore,$663.821$ should be rounded off to $663.8 \text{ g}$.
For example,to find the difference between $0.307 \text{ m}$ and $0.304 \text{ m}$:
$0.307 \text{ m} - 0.304 \text{ m} = 0.003 \text{ m}$
This should be written as $3 \times 10^{-3} \text{ m}$. It cannot be written as $3.00 \times 10^{-3} \text{ m}$ because the result must reflect the precision of the subtraction.