Calculated column using DAX - filldown

Hello,

I need some help please,

I have a table like this:

Now I need to make a hierarchy with the numbers and text.

My ideal look of the table would be like this:

The first level works fine with:

var number = LEFT(TABLE[NUMBER],1)

var text = LOOKUPVALUE(TABLE[TEXT],TABLE[NUMBER],number)

return number &" / "& text

Then I tried something similar for HIAR_2 but it returned an error.

A table of multiple values was supplied where a single value was expected.

Can someone please help me figure this out?

Kind regards,

L