You could use the function coalesce to default to zero when the case property is blank. It would be something like coalesce(#case/folic_acid_received_1, 0) + ....
I tried this. please find the attached photograph. Now if i am filling form I am getting the total like in a one shot I enter the data in ANC 1 then ANC 2 and then ANC 3.
But if i enter the ANC1 data and submit it and then again open form and enter the data for ANC 2. total is not coming.
Your calculation looks correct. I would confirm your case property (folic_acid_received_1) is being updated correctly in the form's case management so that the subsequent time you enter the form it works as expected.
Thank you I found the issue. I am also hiding visit 1 if it if completed. so we have to use coalesce in current question response also like in attached picture