Query on General Visitor via on Priority - Urgent

[sambath2022]

Dear members,
Apologies , if this is not the appropriate forum /thread to ask .,
I need to apply visitor visa for my mother in law ( from Mumbai, India) on priority category ( i.e paying more and visa comes in 5 days etc)
I have completed all the sections of the form and about to pay the fees. System( Gov site) proposes to pay only the standard fees and not the priority fees. not sure how to do this .
Could you please help me with on how to submit/opt the high priority payment route?

Many thanks for your replies

Sam