...I'm sorry, where are you pulling out this statistic from?
He's using the definition of "chronically homeless" as defined in
federal law from a source like
this.
HOWEVER, the number he's claiming both
isn't correct even according to those sources (it's actually 73%), but
he's also misusing the definition of "chronically homeless." To be "chronically homeless" doesn't mean "someone who is still homeless each year", it requires both a continuous year of homelessness (or 4 instances of homelessness within 3 years) AND at least one disability***
for the head of household. This means anyone who is homeless for over a year without a disability (or with a disability but the "head of household" doesn't have one) doesn't count in that given number; a key factor he ignorantly/purposely skipped over.
*** disability as shorthand for "a diagnosable substance use disorder,
serious mental illness, developmental disability (as defined in
section 15002 of this title), post traumatic stress disorder, cognitive impairments resulting from a brain injury, or chronic physical illness or disability"