does the dependent income count if its only social security disability. for a disabled adult. assuming I am abiding by the other qualifying rules

Do not enter the SSA1099 for your child on your own tax return.   Someday if the child has other income  (after school job, etc.) and is filing a tax return, for that tax year he will need to include the SSA1099 on his own return.  Until then, it does not get entered anywhere.

It does not count towards the $5050 gross income test listed below. 

Tests for Qualifying relative:

• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They're a US citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year (exceptions apply).
• They made less than $5,050 in 2024.
• You provided more than half of their financial support.