small potatoes, small beer

A: Mr Barrow said you wanted me?
B: Come in and sit down. Mrs Patmore's got something to say.
A: What's that?
C: Oh, just how grateful I am for your excellent advice.
A: Oh, you've taken it, then?
C: I have. In a way.
A: You've invested in building?
B: Well, she's investing in a building, yes. 
C: I've found a cottage in Perth, and I'm going to see it on Tuesday. It's $300, so it's a big decision, but you've given me the courage. 
A: That's not what I meant at all. I thought you wanted to be in the market to increase your capital. 
C: Well, I'll rent it now and then later, I thought I might take in some lodgers. It's got three bedrooms.
A: Oh, this is very small beer.
C: Mr Carson, it's my kind of beer and I know how to drink it. 
B: But you gave her the idea, didn't you? She's grateful.
C: Oh, I am. It's good to hear advice from a man of the world. 
A: Well, I like to do what I can. 
B: We feel thoroughly protected.