Help w/ Power BI Calculated Columns

i can do it but i dont know how, the database has around 100 columns and 5000 rows.

in the last photo there are 2 plant scorecards, the first one represent the datas for a specific plant that i selected from slicer for every month until september and the last column which is FC(Forecast) is the average forecast per month so in the bottom scorecard it says total forecast for months jan-sep is 335 ( so the 28 is 335 divided by 12).

Also in the last scorecard for month feb and so on its calculated like these: feb=feb+jan, mar=mar+feb+jan, apr=apr+mar+feb+jan and so on

so the problem is that i need to calculate these columns in power bi and i dont know how, and for every single plant that i have its the same situation, so i cant do it manually because i have around 50 plants