Coco nutrient/ppm help

I have Nutrifield A & B coco nutrients that recommends 5ml from each bottle per 2 litres of water, and EC 1.2(840ppm) to 1.6(1120ppm)
but the EC is lower than what they recommended when i mix it all up. I put 5ml from each bottle into 2 liters of water and it came out as
a little over 630ppm, minus the tap water ppm.

Shouldn't putting 5ml from each bottle into 2l of water come out as exactly 840ppm (1.2EC) like their recommendation?
or do they want me to use more?

PPM of my tap water is 0.63.

According to a site i looked at, my ppm meter is Truncheon 1 ms/cm (EC 1.0 or CF 10) = 700ppm

*I've never grown with coco before*

you need to add some calmag to bring your tap water up to .3 - .4 EC before you add nutes. Some nutes assume you start with .4 EC water. That should get you to 840ppm

Yep, as munkee said, bring it up with CalMag. One with trace-elements present is always a bonus.

Alright cool.

Might wait for the plants to show if any cal/mag is needed before i pay the $15 shipping to have that cal/mag stuff
sent here

I feel like this PPM meter was a waste of money when the nute recommendations are based on guess work.

PPM meter is handy. You get a better of idea of whats going in and coming out. With Coco you will end up needing CalMag at one point, so best to grab it now if it suits you if not I guess you could always pick some up.

Also when feeding if the PPM runoff is higher than the input then it is being over fed. The same for if the runoff is lower than the input, raise the feed by about 0.2 EC.

But if everything is good and green just keep an eye on the PPM levels and don't worry if it's over reeding, that can be the salts being washed out the coco.