When you go to make a new brush, because you stated that you choose a general round hard brush, I assume you choose an existing brush from your presets and change it's settings and eventually save those changed settings to a new preset. If you chose this same brush for your second brush (to save), the settings for that round hard brush you initially choose will reset to it's original settings, thereby changing all of your previous settings. This is normal since each preset brush has it's own saved settings.
If you want the new brush to start off with your previous settings, choose the last brush you saved as a starting point for the new brush.
Example:
Note: these settings are just example numbers!
Hard Round Brush - Settings: 10, 24, 56, 29
You make a new brush from the Hard Round Brush and change it's settings to: 12, 30, 52, 24
You name the new brush .........Brush A
Now you want you make a new brush called Brush B.
If your starting point is the Hard Round Brush..............when you choose it again...........it's settings will be: 10, 24, 56, 29