What is really interesting here, that rotmistrz Tyzenhauz and lt. Borejko arrived only by themselves, without any retinue - in fact all nobles in banner arrived in such manner. Normally, officers in such unit in regular army had retinues of 12 horses (rotmistrz) and 6 horses (lt.) which were in fact 'blind portions' from which they took they pay. Also very interesting is bit on last page - 'stawił bojarzyna z muszkietem po dragońsku' - 'send boyar with musket in dragoon's fashion'.
I agree with you, it looks unusual. Maybe in powiatowy troops officers didn't have any extra fees? And keep service only from their own incomes? Similar model was in Russian feudal levy - pomestnaia konnitca. Vorbek-Lettov's memories also includes a roll of Gosiewski's Hussars in Feb 1655, I will put them soon.
I would agree if it would be banner of 'pospolite ruszenie' (noble levy) but district ('powiatowe') troops were enlisted soldiers, usually with better pay than soldiers in state's service ;) Also typical way of creating banners of cavalry was to made if from retinues so list above is really odd. Vorbek-Lettov's memoirs is great source, unfortunately I do not have access to it. He had plenty of information from eye witnesses of events, sadly his son died during battle at Werki and it was great loss of him.
Send me a message on e-mail. I will send you a link to V-L memories (a part of 1968 publication)