Hello

I have a work sheet of mobile sites configurations which its standars to
write is sth like [2220] or might be [224] or even [22].
Currenly to find sum of the equipmets I have to put manually 6 for [2220]
for example. How can I make it Authomatic by formula? I thought about Sum
formula combined with Left formula but as the digits might be 2 digit or 4 in
some cells so there is error as ] can't be sumed. Do you know any better way?

Exp:

[2220] =2+2+2=6
[224] =2+2+4=8
[22] =4