The second value in the curly braces dictates the length of the replacement string. By adjusting the second value to be positive or negative, the alignment of the string can be changed.

string.Format("LEFT:  string: ->{0,-5}<- int: ->{1,-5}<-", "abc", 123);
string.Format("RIGHT: string: ->{0,5}<- int: ->{1,5}<-", "abc", 123);

Output:

LEFT:  string: ->abc  <- int: ->123  <-
RIGHT: string: ->  abc<- int: ->  123<-