Median formula and data variable - Number type is not assignable to this list type

Hello - trying to perform a simple median calculation of the numbers in a field I’m pulling through from Airtable via a data variable. Unfortunately, it doesn’t work and is returning a “Number type is not assignable to this list type” error. I have checked the data resource schema and the field I’m trying to calculate the median for is a number field. Can someone please help me? Thank you in advance!