Low income capitalization rate what does this mean?

[Jane Istre]

I saw this on our county's website. Can someone explain what this means? 

2015 LOW INCOME HOUSING APARTMENT CAPITALIZATION RATE: 10.0% The Appraisal District is giving public notice of the capitalization rate to be used each year to appraise property receiving an exemption under Section 11.1825 of the Property Tax Code for Organizations Constructing or Rehabilitating Low-Income Housing: Property Not Previously Exempt.