ASME Section II, Part D, Table 1A lists Material SA-240 Grade 304L twice, on line numbers 15 and 16. The material properties differ because each entry has different applicable notes. For example, the material on line 15 includes notes G5, G21, and T4. Note G5 is particularly significant as it provides guidelines for calculating allowable stresses differently. Therefore, the same material can have different allowable stresses at the same temperature.

In contrast, Note G5 does not apply to the material listed on line 16, which explains why the allowable stresses are different for that entry.

Please find below the G5 note from ASME Section II, Part D for your reference: 

In the screenshot below, you can see that within the material database (revision 2021) in Autopipe vessel , two different sets of allowable stress values are shown. The first set, without Note G5, corresponds to the material listed on line 16. The second set aligns with the material on line 15, which includes Note G5.
 

You can switch between these property sets by selecting the checkbox “Apply ASME Section II Part D Note G5” in the material section for each component.

Similarly, for SA-240 Grade 316L, the same scenario applies. In this case as well, Note G5 is the key factor that causes the difference in allowable stresses values.