The part of the sentence 'an additional two days' is correct and usable in written English.
You can use it when referring to an extra two days that are added to a period of time. Here is an example: "My vacation has been extended by an additional two days."
The rats were passively trained for an additional two days as described above with one striped wall, before on the third day receiving a probe (Test trial) that now used two black and white striped walls arranged next to each other for the first time.
The FBI sought and obtained a warrant to seize all of Rosen's correspondence with Kim, and an additional two days' worth of Rosen's personal email, the Post reported.
The improved deal includes increasing the redundancy cap from £36,000 to £45,000, and giving an additional two days paid holiday to all staff with over five years' service to "recognise their commitment".
It's earned a reputation as one of the most outstanding sportives the UK has to offer and next year the Wiggle Dragon Ride will be preceded by an additional two days of road cycling for the very first time, to create the Dragon Tour supported by Stephen Roche.
Despite being given an additional two days off work, many Venezuelans shunned the country's beaches this weekend.
He was also told that he would be given an additional two days of punishment each time he refused to stand during the pledge. .
Then, we had an additional two day ministerial which we are not planning but I am totally confident that the membership can manage the business of those two Committees in three days each.
Patients treated with MIC who tested positive for Candida albicans (CA) were switched to FLU and received an additional seven days of treatment for a complete 10-day course, while those treated with FLU empirically and testing positive for CG or CK were switched to MIC for an additional 10-day course of appropriate coverage.
Following the addition of cytokines, cultures were incubated for an additional eight days.
The fresh weight (FW), leaf area, dry weight (DW), CO2 assimilation rates (CA), dark respiration rates (DR), and transpiration rates from 26 day-old radish plants that were grown for an additional seven days at different total pressures (33, 66 or 101 kPa) and pCO2 (40 Pa ,100 Pa and 180 Pa) were measured.
The cells were then pretreated with 1.0 µM CGS21680 for 30 min followed by the addition of 1.0 µM ZM241385 or exposure to SMF for an additional three days followed by staining with F-actin conjugated with Oregon Green488 phalloidin (1∶100) (Molecular Probes, now Invitrogen, Eugene, OR).
