How to manipulate a message's property?

Sorry folks, but today's dumb question:

I already have this:
$globalContext("SCAN_TIME")*2.5

Only to keep things easier I need another node to have that value *2.

So I have a node:

[{"id":"9cefd2571d868370","type":"change","z":"c636aa5a.cc34","name":"","rules":[{"t":"set","p":"delay","pt":"msg","to":"$globalContext(\"SCAN_TIME\")*2.5","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":65,"y":950,"wires":[["9e817108.36937"]],"l":false}]

Down stream from it I want to have a node with TWICE that value in its msg.delay.

I am not sure enough that I can simply do something like:
J$ msg.delay * 2 to double the delay value.

Only that then if ever I change the SCAN_TIME I don't need to edit any nodes.

Thanks in advance.

Simplistically I am wanting this:

[{"id":"8dcd00765893e1a1","type":"trigger","z":"c636aa5a.cc34","name":"Timeout","op1":"","op2":"Off-line","op1type":"nul","op2type":"str","duration":"250","extend":true,"overrideDelay":true,"units":"ms","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":365,"y":1630,"wires":[["9281be2da275833a"]],"l":false},{"id":"27779426545d8713","type":"trigger","z":"c636aa5a.cc34","name":"Timeout","op1":"","op2":"Off-line","op1type":"nul","op2type":"str","duration":"250","extend":true,"overrideDelay":true,"units":"ms","reset":"","bytopic":"all","topic":"topic","outputs":1,"x":365,"y":1670,"wires":[["9281be2da275833a"]],"l":false},{"id":"6f013d1da2275af3","type":"change","z":"c636aa5a.cc34","name":"","rules":[{"t":"set","p":"delay","pt":"msg","to":"$globalContext(\"SCAN_TIME\")*2.5","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":260,"y":1670,"wires":[[]]},{"id":"0676455bee96a4d3","type":"change","z":"c636aa5a.cc34","name":"","rules":[{"t":"set","p":"delay","pt":"msg","to":"$globalContext(\"SCAN_TIME\")*2.5","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":135,"y":1630,"wires":[["8dcd00765893e1a1","6f013d1da2275af3"]],"l":false},{"id":"9281be2da275833a","type":"function","z":"c636aa5a.cc34","name":"","func":"\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":480,"y":1640,"wires":[[]]}]