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Coinbase themselves probably won't care much about the size of your transactions, as long as you have taken care of the required verification steps and your bank account data checks out.
They might not care about the size of the transactions, but they definitely care about the origin of the funds.
E.g. if you want to sell 40 BTC they won´t have a problem if you acquired them legally and can prove it.
If you deposit from a gambling site or a Bitcoin mixer, you are pretty much guaranteed to encounter problems.