Just mixed up some IO, Ca not so good

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Started another pail of IO and low numbers with this one as well.

Made up 20g ro/di then left for a day with a couple of small pumps to aerate, added 12 cups of IO and then left mixing for another day.

Tested today and have:
SG: 1.025 refractometer
Ca: 270 Salifert and 300 twice with ELOS at 71°, thought maybe sample temp so warmed to 78° and got 275 ELOS.
Mg: 900 ELOS
Alk:10.9dKH Salifert
pH: 7.8 using pH monitor and after replacing battery and recalibrating probe.

Either I'm doing something wrong or IO is.