Ai, which is not guaranteed accurate, offers these suggestions. Worth a try...
"To enlarge automatic measure numbers in NCH Crescendo, you can follow these steps:
Open the Score Settings dialog by tapping the Settings button on the Score toolbar tab. In the Score Settings dialog, locate the "Measure Numbers" section.
Within the Measure Numbers settings, you should find options to modify the appearance of measure numbers. Look for a setting related to font size or scale.
Increase the font size or scale value to enlarge the measure numbers.
Apply the changes and check the score to see if the measure numbers are now larger.
If you can't find a direct option to enlarge measure numbers in the Score Settings, you may need to adjust the overall staff height, as this determines the overall scale of staves and could affect the size of measure numbers
Increasing the staff height in the Staff Settings section might indirectly enlarge the measure numbers.
Remember that the exact steps might vary slightly depending on your version of Crescendo, as software interfaces can change between updates."