problem when reading the K C semantics about reval'

[dexter-qjq]

i'm learning something about the semantic of C in K. but i can't understood
syntax K ::= reval(K) [klabel('reval), context(reval)]
syntax K ::= "reval'" "(" K ")" [strict(all(context('reval), result(RValue))), klabel('reval')]
and what's the meaning of this context :
syntax Expression ::= "Call" "(" K "," K ")" [klabel('Call)]
context Call((HOLE => reval'(HOLE)), _) [ndheat]