Reduction in basis of a rental property by depreciation allowed.

[Andrew Sawczyn]

I've had several homes (all initially built or purchased as personal residences) and calculating depreciation always seemed straightforward to me, but I am stumped at the following paragraph :

From IRS publication 946 :

Basis adjustment for depreciation allowed or allowable. You must reduce the basis of property by the depreciation allowed or allowable, whichever is greater. Depreciation allowed is depreciation you actually deducted (from which you received a tax benefit). Depreciation allowable is depreciation you are entitled to deduct...

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I purchased this house in 2004, and rented it for three years, 2008-2012, taking $30,000 in depreciation over four tax years.  From 2012 to mid-2019 it was again my primary residence at which point it was once again converted to rental property.

At this point I must recalculate the depreciation since in the intervening years I made $50,000 of improvements to the property.  Since I have taken the property out of service, does the above IRS guidance suggest that I reduce the basis of the property by the deprecation I have previously used and "from which (I) you (had) received a tax benefit".

That's the only way this makes sense to me, but what does that have to do with our tax code?

Thanks for any insights!