PopulateCache configurable TimeoutInSeconds

[KatiaMarques]

Hello, 
I am obtaining GCP Token from https://www.googleapis.com/oauth2/v4/token, reading the expires_in and storing it in a variable retrieveGcpToken.expires_in.
Then I am creating a PopulateCache  with this value as a TimeoutInSeconds:
<TimeoutInSeconds ref="retrieveGcpToken.expires_in">3540</TimeoutInSeconds>

My question is, without using additional javascript policy, is there a way of taking 60 seconds to the given expired_in, to avoid problems with network time?
For example, retrieveGcpToken.expires_in is now 3600,  is there a way of setting it as 3600-60 using only this policy?

Thanks in advance,
Kátia 

[dchiesa1 · Accepted solution]

I understand the question and I think the answer is NO. 

If I were doing this I would insert the JavaScript step. 

<Javascript name='JS-Calculate-Cache-Expiry'>
  <Source>
    var c= Number(context.getVariable('retrieveGcpToken.expires_in'));
    c-=60;
    context.setVariable('retrieveGcpToken.expires_in', c);
  </Source>
</Javascript>