Expression updates a cell with all records in its specified column separated with commas

[Eso_Surveyors]

Hi, all. this expression :
TRANSFER DETAILS[CUSTODIAN]
fills the cell that i want but concatenates the values of all the records separated by commas, instead of one.
i didn’t expect it to be a LIST, but a single value from the current record being added to another table.
i’m using it in an Action to update with “set the values of some columns in this row”
i’ve tried various other expressions with Select and Lookup and the cell remains empty.

can someone help, please?