See also Rudi's post #71.
You need to find out if you have:
(1) Sodium metaborate 4-mol in which case use the amount specified by Mark, or:
(2) Sodium metaborate 8-mol (this is also known as Kodalk)in which case multiply the amount specified by Mark by 1.354, eg 2.2gx1.354=3g
The quote from Ryuji is about 2 crystalline forms of the same substance,you are correct to say they are the same when dissolved, in this context it is only of academic interest.