Map Labels - Computational?

[syndeysider]

So I have an LLD for disks. A prototype item for disk io spent.

This generates :

Server 1
sda: disk io
sdb: disk io
sdc: disk io

Server 2
sda: disk io

Server 3
sda: disk io
sdb: disk io

I want to create a map for avg disk io for the server for all disks?

Map Label

{HOSTNAME} :{{{HOSTNAME}:custom.vfs.dev.io.ms[sda].avg(600)}+{{HOSTNAME}:custom.vfs.dev.io.ms[sdb].avg(600)}+{{HOSTNAME}:custom.vfs.dev.io.ms[sdc].avg(600)}/3}

I'm not sure if I'm hitting the limit's here?