Change suggested (grey text) in a decimal additional field

Change suggested (grey text) in a decimal additional field

I have added an additional decimal field to a Service Category template.  This is for working hours to be represented in decimal (18 hours 30mins = 18.5 hours).  When I view the field in the template there is auto text in the box that says "e.g. 123.00".  It seems that every additional decimal field I add to templates has this auto text. 

Is there a way to change / customise this text so that it reads something like "Hours must be shown as decimal e.g. 18 hours 30mins = 18.5 hours" instead?