Why the values from Hadoop API doesn't match with the calculated values?

Question

 {
    "name" : "Hadoop:service=NameNode,name=FSNamesystem",
    "modelerType" : "FSNamesystem",
    "tag.Context" : "dfs",
    "tag.HAState" : "active",
    "CapacityTotal" : 250375106560,
    "CapacityTotalGB" : 233.0,
    "CapacityUsed" : 1316515840,
    "CapacityUsedGB" : 1.0,
    "CapacityRemaining" : 171912445952,
    "ProvidedCapacityTotal" : 0,
    "CapacityRemainingGB" : 160.0,
    "CapacityUsedNonDFS" : 64353255424
}

I am using the formula to find the CapacityTotal:

CapacityTotal = CapacityUsed + CapacityRemaining + CapacityUsedNonDFS

Here, the CapacityTotal value obtained using the formula doesn't match with the one given by default from the Hadoop API. Similar is the case for different parameters namely, memoryused etc.

Why is there a mismatch in the values obtained from the Hadoop API? How could I resolve this issue?