Issue with substring function

I have a column named as DEAL_NUMBER which consists below four values,
2442660018000120000000
0000002442660018000124733590XAUUSDM
0000002442660018000124733590XAUUSD
0000002442660018000124733590AUDUSDM
0000002442660018000124733590AUDUSD

After using the substring($in.0.DEAL_NUMBER,12,16) function, the values has been transformed as below,
18000110798858
18000110798858
18000110798858
18000110798858
18000110798858

not sure, why the first record has been replaced by the below deal numbers. Pls help.

Hello,

I do not understand what happens in your graph. Would you be so kind and place your sample graph as the attachment, please? The substring function should return:


0120000000
0018000124733590
0018000124733590
0018000124733590
0018000124733590

Please check the attached graph DealNumber.grf.