EDIT: I changed the answer from a simple decision rule to a more statistical answer.
You would be well advised to use a weights-based approach to handle the problem. One simple way to do so is to multiply the success count of type $a1$ by $\frac{t_2}{t_1}$, where $t_1$ and $t_2$ are the associated totals of the parameter_amount variable: $t_1=54137$ and $t_2=35317$.
So, if the original contingency table was
$$\begin{array}{c|c|c|c}
& \text{Successes} & \text{Failures} & \\ \hline
\text{Type a1} & a & b & a+b\\ \hline
\text{Type a2} & c & d & c+d\\ \hline
\text{} & a+c & b+d & a+b+c+d\\ \hline
\end{array},$$
it should be replaced by
$$\begin{array}{c|c|c|c}
& \text{Successes} & \text{Failures} & \\ \hline
\text{Type a1} & \frac{t_2}{t_1} a & b & \frac{t_2}{t_1}a+b\\ \hline
\text{Type a2} & c & d & c+d\\ \hline
\text{} & \frac{t_2}{t_1}a+c & b+d & \frac{t_2}{t_1}a+b+c+d\\ \hline
\end{array}$$
This way, one penalises type $a1$ for its unfair advantage by changing only one of the four non-marginal entries in the contingency table.
Now, it is appropriate to use a one-tailed Fisher's exact test because the individual observations are independent.
Let $p_1,p_2$ be the success rates (the underlying theoretical ones for which we are conducting inference).
Let $\alpha$ be our chosen confidence level. A $(1-\alpha)\times100\%$ confidence interval for $p_1-p_2$ is given by
$$ \hat{p_1}-\hat{p_2} \pm z_{1-\frac{\alpha}{2}} \sqrt{\frac{\hat{p_1}(1-\hat{p_1})}{n_1}+\frac{\hat{p_2}(1-\hat{p_2})}{n_2}},$$
where the $\hat{p_i}'s$ and the $n_i's$ are the weight-corrected proportions (success rates) and sample sizes, and $z_{1-\frac{\alpha}{2}}$ denotes the corresponding percentile point of the standard normal distribution.
I hope this helps. Let me know if anything is unclear.