[exim] Eval macro help

I have a eval that gets one digit 0-9:

${eval:${substr{-2}{1}{$tod_zulu}}%10}

I think to get 0-4 I could do this:

${eval:${substr{-2}{1}{$tod_zulu}}%5}

Is there a way to get 5-9? It's working with strings, so I am not sure
if it will accept numeric operation.
Could is there simple place I can testing macro like this?

Thank you!