In order for an SPV to not be subject to the Investment Company Act of 1940, the SPV must comply with various exemptions. The 3(c)(1) exemption states that no more than 100 accredited investors can participate in the SPV (there is another exemption called the Qualifying Venture Capital Fund exemption that allows, in certain circumstances, up to 250 investors). Rule 506 of Regulation D (506(b) and 506(c) Offering) is often paired with the 3(c)(1) and 3(c)(7) exemption.
Read more: https://www.strictlybusinesslawblog.com/2017/09/21/3c1-funds-vs-3c7-funds/