No. Cap space is calculated and accrued on a daily basis. The example was 500k cap space per day, in a 200 day season (100 mil cap), where we were only spending 475k for the first 100 days.
Let's say Names was making 25k per day. He was traded 6 days into the season, so he cost us a total of 150k against the cap. If he were instead traded at the halfway mark, he would have cost us 2.5 mil against the cap.
On CapFriendly, you can view the cap tracker for each team, which shows the to-date cap totals for each player:
New York Rangers Daily Cap Tracker - CapFriendly - NHL Salary Caps
Namestnikov was on the roster for 6 days. During that time, he cost a total of 129,032 against the cap.
Since we retained 750k, he will continue to accrue against the cap each day at a rate of 750k / total days in season.