You're talking about "Data Input Sample Time, Before SCLK Clock Off and After SCLK Clock Off"? The datasheet say's those are the minimum times. It doesn't show a maximum so you're welcome to use as long a delay as you like.
Generally you want to use shorter delays because then you can update the display faster and it spends less time blocking any other code you need to be running on your Arduino but it's probably wise to go a bit over the minimum times, especially when you're troubleshooting. If there's a maximum of course you also want to stay under that but in this case there is not.
I'm also doubtful whether that specification even applies to that part of the code.