Wondering what these two codes mean. Force filter. 180825 | GFPF

Background Pony #150A
The first is your user ID, and the second is your force-filter ID.
 
Not sure what the specific force-filter IDs mean.
Rene_Z
Non-Fungible Trixie -
My Little Pony - 1992 Edition
Wallet After Summer Sale -
Not a Llama - Happy April Fools Day!
Artist -

The ID is simply the ID of the filter, which you can access with https://derpibooru.org/filters/<id>. The speecific filter is not public so you cannot see the filtered tags.
 
You can check if a forced filter is currently applied to your account by visiting your profile. If so, it will contain the text “Forced Filter: <name of filter>”. If not, you don’t have a forced filter applied to your account. This change was made 4 days ago.
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