If Nozomi constructed a copy of line segment \( \overline{AB} \) starting from point \( B \), point \( C \) would be positioned such that \( \overline{BC} \) is congruent to \( \overline{AB} \). Therefore:
- \( \overline{AB} = 22.3 \) millimeters.
- Since \( C \) is at the endpoint of the copy of \( \overline{AB} \), the length of \( \overline{AC} \) would equal \( \overline{AB} + \overline{BC} \).
This means:
- \( \overline{AC} = \overline{AB} + \overline{AB} = 22.3 + 22.3 = 44.6 \) millimeters.
Thus, the measure of \( \overline{AC} \) is 44.6 millimeters.