CAGE is an index to a large amount of data so that the whole name and address don't have to be repeated ad-infinitum.
I called the CAGE organization once about Parker. Very nice people. Turns out Sherwin-Williams was the number one holder of CAGE code numbers. It also turns out that some QA people at Parker say "CAGE what?" Normally the CAGE registration is handled through legal or business departments as they are the ones who applied in the first place, so those are the place to call. Some companies (McMaster Carr) are smart enough to put the CAGE on their website.
The point is to provide traceability to the level that traceability is required. Buying Parker hose - use the Hose Division CAGE code so when you dial the telephone number for that CAGE code someone who can sell you Parker hose will answer the phone. If you want a delay, use the top corporate number.
Be aware that every place may have multiple codes. This is because some users want to record that they dealt with a specific facility. If this is important for part traceability it may be marked on the part documentation. Some, like Sherwin-Williams, have multiple local outlets and users may want to record the exact one the credit card was used.
In multi-level organizations each CAGE entry should list the parent, but this is up to the CAGE applicant and they don't often do this.
