Maybe this link would help.
https://photography.tutsplus.com/tutorials/understanding-using-ansel-adams-zone-system--photo-5607https://www.techradar.com/news/the-a-to-z-of-photography-exposure-compensationA plus (+) setting will make your image brighter than the 'standard' exposure, while a minus (-) setting makes an image darker, with each movement up or down the scale recorded as a 'stop', or an increment thereof. A full stop adjustment will double or halve the exposure, but most cameras offer intermediate 'half-stop' or 'third-stop' increments for more subtle adjustment. I, II, [III, IV, V, VI, VII,] VIII, IX , X normal metering exposure centred on zone 5 the mid tone detail +/- 2 stops.
I, II, III, IV, [V, VI, (VII), VIII, IX ], X metered on the highlight zone 7 your subject is under exposed 2 stops
make it brighter +1 exposure compensation
I, II, III, [IV, V, (VI), VII, VIII], IX , X +1 exposure compensation subject under exposed 1 stop
I, II, [III, IV,(V), VI, VII], VIII, IX , X +2 exposure compensation normal exposure.
ok how about if the highlight is in zone 8
I, II, III, IV, V, [VI, VII, (VIII), IX , X] ok subject is now black
I, II, III, IV, [V, VI, (VII), VIII, IX , X] +1 exposure compensation subject in shadows highlights not blown
I, II, III, [IV, V, (VI), VII, VIII], IX , X +2 exposure compensation highlights still not blown subject under exposed 1 stop.
if the brightest highlight was zone 6 then you would be over exposing the subject by 1 stop with 2 + stops compensation.
If you are metering off highlights then it seems adding +2 to the value would ensure they don't blow
if metering the subject then -1 would allow for 3 stop higher highlights instead of the normal 2 stops with detail.
if you are pushing to the right then +1 stop on the subject would give just one stop for highlights in the jpeg but 2 stops can be recovered from the raw.
Is that confusing ?