You described exactly what to do, try it again, it takes a while to get familiarized with the tools, but the learning curve isn't too steep. Watch a couple of tutorials, TES5Edit and xEdit tutorials are just as good for tutorials and they've been around much longer, basically the same as SSEEdit. [ECZN:0001FA4C] ECZN stands for EncounterZone and the number next to it is the FormID of the record, the two first numbers e.g. 00 represents the place in the load order in this case it means the FormID belongs to Skyrim.esm but it is present in Dawnguard.esm also, the base record is present in both plugins, had it been exclusive to Dawnguard it would have started with 03 if it's third in your load order. Type in the FormID in the search field, top most left field, and it should take you directly to the record mentioned, open the brackets in that record to get to the subrecords, just as you would in regedit or explorer tree. Hope it helps