Pulldata() on public survey doesn't return values

[AyeletGreenberg]

I created a simple survey and used the pulldata() function to return values of room size.
It works well on the app and returns the values for the room size from the csv file, but it doesn't work in a browser. Instead it displays the string "NaN" (regardless if I'm signed in or not).
The survey is set as public, and everyone can submit their answers. 

https://survey123.arcgis.com/share/c2b9944090194f38bc326d6f54c23247 

How can I fix that?
Thanks

[JohnathanHasthorpe · Accepted solution]

Hi Ayelet

The issue is that you are using a + to concatenate your string:

      ${RoomSize} +  " Sq ft"

The webform requires that you use concat(), so please try the following:

      concat(${RoomSize}, " Sq ft")

Cheers

John

[IsmaelChivite]

[AyeletGreenberg]

Thanks. canadianclimate it works now. 
I have another question about this form.
When the Room Number is 'Other' I don't want the (relevant) Room Size to appear because it has no values.
Because all the room numbers are 4 digits long I used this formula: 
string-length(${RoomNumber})>0 and string-length(${RoomNumber})<5
What would be the right way to do this when the string length vary?

Thanks