hey man, i just looked at graph 5.4.1 at it shows MAUW IGE hover ceiling on standard day at 7000 ft PA, with temperature at approx +1C, so that fits in with standard lapse rate of 2C per 1000 ft from ISA .
At 1250lb hover ceiling is about 9300 ft PA on standard day, and temp about -5C so that more or less checks as well.
either read across from left to actual temp at that pressure altitude and then down to find max weight for that PA or start at actual weight and read up to actual temp at altitude then across to find relevant PA
remember pressure altitude is altitude indicated with 1013 set without a temperature correction, if you do correct for temperature then you have a density altitude
hope this helps
regards
CF