Got an error

⚠ Your current PHP memory limit of -1 is quite low, if you experience blank pages please consider increasing it. Check Transposh FAQs http://transposh.org/faq/#blankpages

I got error after update. But stil all worked fine. Is error correct?
Anyways
So i changed server from 512 to 720mb something.
I updated and got again this error! How much is needed?

Can in that page be put link to some good answer about how to change that?

I have nginx and i thought it wont eat a lot ram but i could then increase if error is correct.