The ID Path is the value of the unique assembly component path that Creo uses to identify feature IDs within components starting at the top-most assembly and working recursively through the sub-assemblies. Each sub-assembly level is delimited by a "."
In the above picture, the P2F1866 component (boxed in red) with the 'ENCLOSURE_FRAME1_SUBFRAME' compound designation has an assembly component path of '"13.11.6". To better understand this ID Path, let us look at the model tree (shown below).
At the top-level, RF_SWITCHING_CABINET.ASM has a sub-assembly named ENCLOSURE_STRUCTURE.ASM, which has a Feature ID of 13 (boxed in red). ENCLOSURE_STRUCTURE.ASM contains a sub-assembly named P2F1866HF_FRAME.ASM which has a Feature ID of 11. Within the context of the ENCLOSURE_STRUCTURE.ASM, the lowest P2F1866.ASM component has a Feature ID of 6. Therefore, the ID Path of the lowest P2F1866.ASM is 13.11.6.