This parameter does not appear in the current integration implementation.
You can ask this question to Checkbox technical support.
They probably have the type of operation of the fiscal check that you write about - it appears only for payments with type=CARD, and in the case of "Payment" - payment with type=CASH is transmitted.
From our side, I see only a refinement so that "Pіslyaplata" is transmitted with the CARD type (if it is normally accepted by the Checkbox API) - the implementation of the setting will take 1 hour
If there is such a parameter in the API - provide information about it - we can finalize the corresponding setting in 1 hour.
In the current documentation
https://docs.google.com/document/d/1Zhkc4OljKjea_235YafVvZunkWSp6TCAKeckhgl8t2w/... I don't see an explicit setting that allows this.
You can similarly address this claim to Checkbox API technical support. We do not pass any parameters to them regarding these signatures - accordingly, the entire check output is generated on their side.