If one thinks of the operator `stit' in stit theory [see \textit{N. Belnap} and \textit{M. Perloff}, ``Seeing to it that: a canonical form for agentives'', in H. E. Kyburg jun., R. P. Loui and G. N. Carlson (eds.), Knowledge representation and defeasible reasoning, 169-190 (1990; Zbl 0743.68024)] as a modal operator, we may ask how many distinct modalities there are. The answer depends on the complexity of busy choice sequences (sequences of infinitely many non-vacuous choices made in a finite time) allowed in models. The paper defines a degree of complexity on chains of busy choice sequences, and hence on models, and proves that for all \(n\geq 0\), if the models are those of complexity \(\leq n\) then there are exactly \(4n+ 10\) distinct modalities, each of length \(\leq n+ 2\).