How add data obtained and display the total?

Here is the code, i want to add all the data previously obtained each day and display the total. please help

% Enter your MATLAB Code below
% Read Output Water Quantity over the past month from a ThingSpeak channel and write

% the average to another ThingSpeak channel.

% Channel 1035265 contains data from the MathWorks water supply station, located

% in Natick, Massachusetts. The data is collected once every day. Field

% 3 contains output liquid quantity data.

% Channel ID to read data from

readChannelID = 1035265;

% Output Liquid Quantity Field ID

outputliquidqantityFieldID = 3;

% Channel Read API Key

% If your channel is private, then enter the read API Key between the '' below:

readAPIKey = '';

% Get Output Liquid Quantity data for the last 30 days from the MathWorks water supply

% station channel. Learn more about the THINGSPEAKREAD function by going to

% the Documentation tab on the right side pane of this page.

meter_reading = thingSpeakRead(readChannelID,'Fields', outputliquidqantityFieldID,'NumPoints',1,'ReadKey',readAPIKey);

% Calculate the Cost
Billing_cost = 5* (meter_reading/1000);

display(Billing_cost,'Total Billing Cost (INR)');

% Start by setting the channel ID and Alert key. All alert key start with TAK.

data = thingSpeakRead(1035265,"NumDays", 30);
formatSpec = "The Water consumption bill is: %d,%d";
A1 = 5* (meter_reading/1000);
A2 = meter_reading
apiKey = 'TAK14ZOZGAXZQMR05';
alertURL = "https://api.thingspeak.com/alerts/send";
options = weboptions("HeaderFields", ["ThingSpeak-Alerts-API-Key", apiKey ]);
alertBody = sprintf(formatSpec,A1,A2)
alertSubject = sprintf(" Water consumption exceeded 100 kl!");
if meter_reading >= 100
    webwrite(alertURL, "body", alertBody, "subject", alertSubject, options);
end