Maximum Value from Tables/Arrays

Hello, 

I am having difficulty applying the solution here: 

https://community.ptc.com/t5/Mathcad/Maximum-Value-from-Tables/td-p/999431

I have set-up a minimum example here with two arrays. When I try to get the maximum, an error is caused by the range variable i, "This value must be an integer". 

I am using PTC Prime 9. 

Appreciate your help!