a several building blocks were already introduced .e.g dynamic selectors.
From your screenshot we do see that the population part is driven by a for each row acitvity.
The for each row activity has an output field called index which represents the current loop number.
So this information can directly be used for the dynamic selctor e.g.
assign Activity - within the for each row block:
strTableRowPart= (index + 2)
- we refer to your screenshot TableRow=‘2’
and the dynmic selector could look like
<webctrl tableRow='{{strTableRowPart}}' tag='input' />