IMHO the SPP closes at the end of the 5 day period, not the beginning, so can decide whether to subscribe when about half way through and have an idea of the price.
"a 2.5% discount to the Volume Weighted Average Price (VWAP) of fully paid ordinary Nearmap shares traded on the ASX during the five trading days up to and including the closing date of the SPP (Tuesday, 29 September 2020 to Monday, 5 October 2020)."
From booklet: SPP Closing Date 5:00pm Monday, 5 Oct. 2020