UNOS is Southern Hemisphere and ONUS is Northern Hemisphere.
The errors are maximum i.e. 30 degrees at the poles and decrease by 10 degrees of error towards East and West where they are nil.
They are used for compass turns if your gyro fails on your DG or HSI.
ANDS and SAND are to do with an off centre C of G on the compass combined with magnetic dip. ANDS is for the Northern Hemisphere and SAND for the southern. They occur as a maximum on East/West heading and are nil on North/South headings.
So for ANDS i.e. Northern Hemisphere on a heading of East . If you accelrate from 100Kts to 120Kts you need to bear in mine, whilst navigating on the compass IMC, that the needle will deflect to the North. If you then decelerated it would deflect to the South. When you settle the speed, provided you haven't deviated on heading, the needle will point to East again.
I hope that has answered your question.