First, you can't hide the fact that you only sold 32 copies of the software - you'll get called on that sooner or later. You can, however, make that sound better by demonstrating why it should not be held against you - limited effort to date in trying to sell.
Second, your concern about a patent is very relevant. A prudent investor will want to know how hard it would be for someone to copy you - and if your answer is "really easy" then there's no investment. Getting around that might have been market capture - that is, you already hold a significant amount of the market, and therefor you have history on your side, but sadly, that isn't true.
Third, you need to know what you intend to do with the money. Investors are generally not interested in just giving companies money for no reason - they want to know what you intend to do with the money. You need to show that you have a plan and a need.
Regarding valuation (which is what this question ultimately boils down to), we need to look at what you have.
You have a product which you developed that has some (small) inherent value. Let's say it took you 1000 hours to write, test, and package it. That gives you a value of somewhere in the $25,000 range to reproduce that work.
You have 32 clients at a rate of $20 per year, or $640 of income per year. We'll assume that you've spoken to at least some of them (and if you haven't, you ought to) and confirmed that they would be willing to pay $60 per year, which bumps this number up to $1,920 annually.
So your total value is somewhere in the range of $25,000 to $30,000. If you start asking for more money than that, you'll have a problem, because there would be no way to split the equity in a reasonable fashion.
What you can do to boost your valuation is to get more clients - fast. If you can demonstrate that you're chasing teams and getting them to sign on (i.e. your conversion rate is 50% instead of 10%, and you have a sampling of 100 teams to base this on), then you've accomplished two things:
- Your product can sell - if you can get the information in front of potential buyers, they're really interested in buying it, at the price you want to sell it;
- You have a growing customer base, which means that the $1,920 in annual income has grown over a month to $4,920 annually.
Both those factors will allow you to push the valuation a bit higher than the strict numbers justify - i.e. if you valued it at $30,000 today, then with growth patters, you might be able to get it up to $50,000 or perhaps a bit more.