To find the score of the second-place gymnast, we can subtract the margin by which the first-place gymnast won from the first-place gymnast's score.
The first-place gymnast scored 28.948 points and won by 0.99 points. Therefore, the score of the second-place gymnast can be calculated as follows:
\[ \text{Score of second-place gymnast} = \text{Score of winner} - \text{Margin of victory} \]
Substituting in the values we have:
\[ \text{Score of second-place gymnast} = 28.948 - 0.99 \]
Calculating the above expression gives:
\[ 28.948 - 0.99 = 27.958 \]
Thus, the second-place gymnast scored 27.958 points.