Ok, just looked at the IPO Prospectus to make sure and you're right, the floor is always 4.0%. I'll update.
"Thereafter, the ""Variable Rate Dividend Period'' relating
to a Variable Rate Dividend Payment Date will be the period from but not including the preceding
Variable Rate Dividend Payment Date through and including the related Variable Rate Dividend
Payment Date, and dividends will accrue from Variable Rate Dividend Period to Variable Rate
Dividend Period at a variable rate equal to 3-Month LIBOR plus 0.50% per annum, but not less
than 4.00% per annum.