What does the following notation mean: R$2.\{$A$2\}$ $\backslash$times $2286$; R$1.\{$A$1\}$

A$2$ is a partial key for the weak entity R$2$ and is identified by A$1$

All values of R$2.$A$2$ must be in the set of values found in R$1.$A$1$

All tuples in R$2$ are a subset of R$1$

A$2$ is a key attribute for the candidate key A$1$