question about passing complex strings in Parallel

[Saint Michael]

This is related to parallel, but we can replicate the issue in plain bash.
in this code:
data="'1,2,3,4','5,6,7,8'"

# Define the processing function
process() {
echo "There are $# arguments."
    echo "They are: $@"
    local job="$1"
    shift
    local a="$1"
    shift
    local b="$1"
    shift
    local remaining="$*"
    echo "Arg1: '$a', Arg2: '$b'"
}
process "$data"

how can I get my (a) and (b) arguments right?
The length of both strings is unpredictable.
a="1,2,3,4" and b="5,6,7,8""