how do I write a formula in an email template, ie: ${customer.consolDaysOverdue - 60} tried multiple different formats but no luck so far

Try something like this

<#assign days_overdue_minus_sixty = customer.consolDaysOverdue - 60/>

Then you should be able to use that variable in your template

${days_overdue_minus_sixty}

Hi Jen, thank you for reply, I tried that and received:

The template cannot be saved due to the following errors:

The following has evaluated to null or missing:. ==> days_overdue_minus_sixty [in template "content" at line 3, column 98]. . ----. Tip: If the failing expression is known to be legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present#elsewhen-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??. ----. . ----. FTL stack trace ("~" means nesting-related):. - Failed at: ${days_overdue_minus_sixty} [in template "content" at line 3, column 96]. ----

Does customer.consolDaysOverdue exist?

it does exist,

Can you post the part with your #assign and using the variable?

I pasted at the top of the template, just as you had typed it