Store.size vs disk.indices - disk usage


I have a 3 node elastic cluster.
The output of 'localhost:9200/_cat/indices?v' shows up the store.size for indices a & b
the sum of store.size of a & b is much higher than the disk.indices from the command
curl -XGET localhost:9200/_cat/allocation?v.

So which one of these ( disk.indices or sum of store.size) is the actual disk usage of all the indices per node ?

Thank you in advance. Greatly appreciate any help.