Rectify 'up to 60 minutes' to 'at least 60 minutes'

README

@@ -41,7 +41,7 @@ where
 
 <threads per node> and <blocksize> will be chosen optimally for best
 performance.  <bytes per thread> will be chosen so that the write and
-read phases run for up to 60 minutes each.
+read phases run for at least 60 minutes each.
 
 Results will be evaluated by looking at the "WRITE" and "READ" sections
 in the table output from elbencho on stdout.  The row "Elapsed time" in
@@ -77,7 +77,7 @@ where
 
 <threads per node> will be chosen optimally for best performance.
 <bytes per thread> will be chosen so that the write and read phases runs
-for up to 60 minutes each.
+for at least 60 minutes each.
 
 Results will be evaluated by looking at the "WRITE" and "READ" sections
 in the table output from elbencho on stdout.  The row "Elapsed time" in
@@ -112,7 +112,7 @@ where
 
 <threads per node> will be chosen optimally for best performance.
 <number of files> will be chosen so that each phase; create, stat, and
-delete; runs for up to 60 minutes.
+delete; runs for at least 60 minutes.
 
 Results will be evaluated by looking at the "WRITE", "STAT", and
 "RMFILES" sections in the table output from elbencho on stdout.  The