Power Bi running total and power pivot

Hello,


Also asked on Mr Excel ;

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I have running total formula whch works perfectly well in power pivot but I can't get it to work in power bi, which I'm trying to get to grips with,

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when the same measure is used in power bi, it just returns the 'row' value , ive tried adding columns and get the same result, just each row repeated. What's the difference? have attached a small sample file which I had loaded into power bi.
Richard.