Hydrostatic Testing for Sub-Sea Pipelines

I was reading in the OSF101 code about Hydrotesting, and here is what i found out,

1) For pipes with reduced utilisation of the wall thickness, the test pressure Ph maybe reduced as permitted in section 5D 400.

2) The test pressure Ph for all other pipes shall, in situations where the seal is made on the inside or the outside of the linepipe surface be conducted at the lowest value obtained by utilizing the following formulae:

Ph= (2.tmin / (D - tmin) ) . min[SMYS. 0.96; SMTS . 0.84]

3) In case where the specified corrosion allowance restricts the test pressure due to mill testing capacity, the test pressure shall be Ph = 1.5 Pdesign

-----------------------------------------------------------

I aslo have read in the other hydrotesting thread about the 1.5 factor for the piping hydrotesting so i was wondering about the seal inside or outside of the linepipe surface in #2, what does it mean ?

also what and when is the specified corrosion allowance restricts the test pressure due to mill testing in # 3 ...actually what does all this mean ?

once again what is a mill test ? What does the word mill mean ? millimeter ? (obviously not)