Text.PadStart Function in Power Query
The Text.PadStart function returns text of a specified length by padding the optional character at the start of the given text. An optional character can be used to specify the character used for padding. The default pad character is a space.
Syntax
 Text.PadStart(text as nullable text, count as number, optional character as nullable text) as nullable text 
Example:
Power Query M
let
    Source =Text.PadStart("Ashish", 10)
in
    Source The output of the above code is “ Ashish”.
Power Query M
let
    Source = Text.Length(Text.PadStart("Ashish", 10))
in
    Source  The output of the above code is 10.