I don't understand free-tier!??

[greg]

Good question!

This answer makes me think yes (and logically 512mb+256mb === 256mb+256mb+256mb) but you may want to wait for confirmation:

Account Eligible for the new free-tier

Yes, you can create 3 VMs of shared-cpu-1x with 256MB per month or you could create one VM with additional memory. We bill ~5$ per additional GB but since you’re using 512MB (256MB additional memory) it should be even lower than that.