The CPT code descriptor does not indicate "
up to" it is
"each 15 minutes"
The transmittal below indicates that a single unit should
represent total time = to or > than 8 minutes
(i.e. 1 unit represents 8 thru 22 minutes)
To get the second unit it appears that time would need
to be = or > 23 minutes total.
A CPT Assistant from December 2003 indicates:
"a substantial portion of 15 minutes must be spent in performing
pre-, intra-, and post-service work".....If only a few minutes
are spent performing the manual therapy technique, either
the code should not be reported, or append mod -52.
CMS Transmittal 1019, Aug 3, 2006; Change Request 5253
http://www.cms.hhs.gov/transmittals/downloads/R1019CP.pdf
Hope this helps,