"Maintenance and support of project x, including major refactoring yy modules to allow integration with zz. This allowed the company to progress with MI reporting solution / comprehensive unit test framework / some other usefulness, resulting in a reduced total cost of ownership, a saving of approx $4m."
Repeat per project.
Mostly fixing bugs
Spin and emphasize (without lying) all the stuff that is not bugs in the same way.
Did you show anyone else how to fix it? That's team leading / mentoring (but don't lie).
Don't think of what you've been doing as defect resolution; think of it in terms of business benefit.
Aside - fix any spelling mistakes ("there", "their"). They will leap out far more at anyone reading your CV than bigging yourself up in the text. Your CV is a sales brochure and needs to be polished.
A number of commenters have pointed out that a developer would likely not know the $ value of their contribution, or maybe even the project as a whole. @puck points out that it may be detrimental, as an employer may not want their costs made public.
These are all valid points, and I generally agree, but note that as $ was mentioned in the original post, I included it in my example. For anyone uncomfortable with putting financial figures, try using another performance metric, e.g. (from my own CV):
Reduced database transactions from 4bn/week to 2.8bn/week leading to a
direct reduction in hosting fees.
[I know exactly what that represented as a cost saving, as the CEO of that client was publicly ecstatic].