Please see In The Zone - Part 2 (and Part 1) where I give a thorough explanation of the Activation Zone. Short explanation - if there’s no way you could, even theoretically, walk from the summit to where you are without dropping more than 25m (82 feet) you are outside of the AZ. Note that doesn’t just mean being no more than 82’ lower in elevation. An adjacent rise the other side of an 82-foot dip is not valid. There is no horizontal limit. There are AZs that are literally miles across!
Looking at the W3/PH-006 summit page and following the link to CalTopo it seems to be a simple one. (I shalln’t paste an excerpt as I’m not sure of the legalities)
See also the Lists of John entry.
Listed height is 1070’, so the edge of the AZ is the contour surrounding the summit 82 feet lower, at 988’. Without taking a guess at exactly where the 988-foot contour would run to play safe would be to stay uphill of the 1000-foot contour. But maybe that T junction about 250m east of the summit is just inside?
Don’t rely on reading your 988-foot limit off a consumer GPS (usually wrong, not least because most often they read ellipsoidal height, never mind the noise) or pressure altimeter (maybe not so bad if you can calibrate at the actual summit and walk down, or some other rock-solid nearby calibration point).
We have summits with AZ spanning even national borders! In that case you would just take account of changing jurisdiction (vary your call sign, obey local spectrum regs), but for W3 → W3 of course that is of no consequence.