Bonus Depreciation Calculation as per new seeded depreciation methods

Hi,

We see that new seeded bonus depreciation method available. Example MACRS 50B HY .

We need clarity on the bonus calculation.

If an asset is added in Dec-14 (Assuming Feb-Jan to be the calendar) for $20000 having a 5 yrs life.

As per MACRS HY 5 years the depreciation is 20% for first year. Depreciation - $20000 * 20% = $4000. This amount seems to be right.

When we use MACRS 50B HY, the depreciation rate is 60% (this has the bonus depreciation built in the method)

$20000 * 60% = $12000

As per IRS requirement the bonus depreciation is 50% flat on the asset cost which is $20000 * 50% which is $10000

Depreciation for the year - $ 4000

In total we expect $14000 to be charged and instead the new method is charging $12000. Can someone clarify if they had a similar situation or clarify how the bonus depreciation was handled.