Store a string array in a array pv variable in the process model in the correct format

Hi,

I have a rule which returns an array of strings in this format:

List of Text String: 4 items (The number of values can differ depending on the number of values present in the database for a particular request)

"60,70"

"60,70,72,74"

"72"

"70,72,74"

When i use the same rule in the process model to store in a pv(process variable) having multiple checked then i expect the following value for the pv:

60,70, 60,70,72,74, 72, 70,72,74

Instead i get the value which considers each value as a different input to an array. Like this:

60, 70, 60, 70, 72, 74, 72, 70, 72, 74

Can anybody help me out with this?