Hello.
It sounds like you are talking about our S10V2F12 step-up/step-down regulator. Like it says on its product page:
The plot at the bottom of that regulator’s page shows about how much current you can expect the regulator to handle at different input voltages. It looks like since your system nominally needs about 300mA, you would be pushing the limits of this regulator, regardless of what your input voltage is. If you tell me what voltage you are using as an input, I might be able to recommend a more appropriate regulator.
Also, in an email you also sent to us about the same question, you asked about paralleling the output of two of those regulators together. Please see this post, which explains why that is not a good idea.
-Jon