The total for the 8.5 year period is 441,176 units, which I believe is approximately 135% (more than double) higher than the current target.
Almost 60% of the units are targeted at low and moderate income households while 40% are for HH making more than 120% of the area median income
About half of these units are for the projected growth in population and half are to "catch up" on existing shortages: to reduce the number of overcrowded and cost-burdened households and to target a normal supply of vacant units. These catch up requirements are the result of recent state legislation to relieve housing challenges for current low and moderate income residents and are new to this round of RHNA allocations.
Palo Alto should expect to get a higher % increase as goal. The ABAG RHNA allocation committee criteria (not final yet) target above average allocations for 1) cities that are high opportunity areas and 2) cities that have an abundance of jobs relative to housing. I expect Palo Alto would score high on both of these criteria.
Whatever allocation Palo Alto ultimately gets will need to be planned for in the Housing Element update due in 2022. This will be a major work element for staff and the council in 2021. The Housing Element needs to contain credible and feasible sites for housing as well as an array of policies to meet state goals.
This is where local control can come into play as Palo Alto can adopt its own plan to meet the targets though it has to be credible and feasible.
Current and future housing proposals should be considered with this knowledge about Palo Alto's upcoming RHNA goals.
A final note.
The HCD determination was not based on the ABAG job and population growth forecast. If it had been, the target likely would have been 100,000--150,000 housing units higher.