We want to send the total value as a number via query string

On the site of our client we have a couple of ‘donation’ forms made with GF and 1 main donation form → all other forms are small quick action forms sending their info to the main form were you sort your personal information and get send for payment.

After years they have decided to move to another payment processor for their donations and external forms for those donations were included with that. So the idea now is to use the old quick forms, as they are still holding all correct styling and data and on submit send it to the new external forms with data (frequency and amount to donate) in querystring so they can get their donations.

This all works reasonably well except for the total amount. In the original setting, the quick forms just send all the fields, and the actual donation form managed the rest via conditionals etc.
Due to the changes we have multiple form fields that could add data to the same querystring parameter, that will send a mess of different field values and will almost always be incorrect. So there is a total field that could solve all our problems. it shows the correct amount every time - we will hide it with CSS - but were other parameters were very good with &t={Frequency:19:value} sending the required (by 3th party form) input value, &bf={Total:22:value} will still send bf=€+15%2C00 (€15,00)
Can we format that mergetag? We would like this to be send as 15 or if its a decimal 12.50

The total field doesn’t support the value modifier, you need to use the price modifier instead, it outputs the amount without the currency formatting.