Statistics profile variable size limit

Does anyone know the data type of a variable defined in a statistics profile? What I am really looking for is what is the max size? And once that size is reached what happens? Does the variable flip to 0 or does it cause an error?

The reason I ask is I am counting the total number of Credit card transactions an iRule processes and I was wondering if I should flip the total to 0 when it reaches a certain value or if it is done automatically.

I guess I should also ask the same for the variable within the irule too ( ::total_tran ).

when RULE_INIT {
 Set the statistics profile name
set :ROFILE_NAME "Tm_Statistics"
set ::total_tran 0
}
when CLIENT_CONNECTED {
incr ::total_tran 
STATS::set $:ROFILE_NAME "Total_Transactions" $::total_tran
}

Thanks!!