Potentially, you can apply the same predicted probability to three groups:
All Adults. If you see a way for your selected values to apply to all 260m adults, you can regard those values as targets to hit to increase (or decrease) the 17% (.17) and 45m numbers. To ensure they apply, hold constant every socio-demographic variable.
If you select values that can't apply to all adults (e.g., everyone can't be 18-34), no worries. The target group is limited to those with your socio-demographic selections. So if you choose Age ("18-34"), Urbanicity ("Suburban"), and Education ("BA/BS+"), the result will apply to 7m adults.
Specific Individuals. If the values you choose are your own, or those of someone you had in mind, the resulting estimate will be your, or their, predicted probability.