I suspect you are overestimating what you are entitled to.

20% of the founding equity rarely turns into 20% of the final sale price of the company. Normal, healthy subsequent investment could easily dilute the founding shares 2:1 or 3:1. If the company goes through especially bad times -- a near bankruptcy followed by a last-minute bailout by investors, not unheard of in the last few years -- the founding shares could easily be diluted 10:1.

Add in a modest management carve-out from the sale, and your 20% amounts to 2-5% of 90% of $64 million, or $1.2-$2.9 million.