ALK reading 3 DKH higher than tested amount

Wondering if somebody could help me out in this forum. Just received mine today and got it all set up and the reading is 3 dkh higher with the alkatronics.

Alkatronics is 12.5
Hanna and Red Sea is 9.5

I mixed the provided 250ml bottle regent with 1000 ml of RO water. Did it by weight, 1000 ml = 33.8 oz plus 25 ml from the bottle 8.5 oz gave me 42.60z I think? bottle has a little or than 250 ml.

Calibrated Channel A twice 57 ml twice
Calibrated Channel B twice 8.5 ml twice (I did notice the .5 ml per line)

PH probe calibrate to both 7 ph and 4 ph.

It seems pretty simple put its way off. Anybody have any ideas?

I think you mixed the reagent incorrectly. I made the same mistake initially.
"Now carefully fill upp with reagent to the readings of exact 400g.
• DO NOT remove the canister from the scale, let it be, still reading 400 g of
course, and now add RO-water until you read exact 2000 g at the scale. Done!"

So it should be 250ml and then fill the rest to make it an even 1000ml which would be 750ml water.