Match formula limit change mid year

How is the match allocation limit determined for mid-year match changes with respect to the compensation limit?

For example:

Match is funded per pay period. Match formula changes July 1 from 100% of 10% to 100%  of 4%.

Pt earns 30k/month and contributes 10% for 1st 6 months and 4% for last 6 mo.

  Jan - June - match allocation =  18,000  (180,000 x 10% )

  July - Dec - match allocation =  4,200 (105,000 x 4%)

Total match allocation = 22,,200.

Option 1 - The  per pay period match total of 22,200.

Option 2 - is the match limited to (10+4 )/ 2 = 7% x 285,000 = 19950

Option 3 - Something else?

Thank you for your responses.

If it is calc'd per pay period then it is per pay period (period ?).  Option 1. 

I think such changes have the potential to be discriminatory.