Start of Alignment showing previous chainage after truncating

Hello,

I had designed an alignment with a starting station as say 19+600. Now as per client requirements, our scope has been revised to start from later chainage of 19+900. Using Element method, when I truncate the horizontal alignment to 19+900, in display the alignment shows from 19+900. But while creating a master string and doing the vertical profile, the option of new chainage at datum shows the previous chainage of 19+600 only. Am I missing something ??