I'll just do the entire quoted text, for completeness.
(1) यदक्षरपदभ्रष्टं मात्राहीनं तु यद् भवेत् । तत्सर्वं क्षम्यतां देव नारायण नमोऽस्तु ते ॥
(2) विसर्गबिन्दुमात्राणि पदपादाक्षराणि च । न्यूनातिरिक्तं यत्किञ्चिदाभिर्गीर्भिरुदीरयेत् ॥
These two together are quite common to recite at the end of stotrams.
"Whatever syllable or word is incorrectly uttered, whichever sound is devoid of the correct length, O Lord Narayana, please bear with them all, obeisance to you."
"The placement of visargas (अः), bindus (अं), lengths of sounds, syllables in words and in quarters (of stanzas), and whatever deficiencies and excesses may appear in this speech."
(3) आभिर्गीर्भिर्यदतो न ऊनं । ४ । आप्यायय हरिवो वर्धमानः । यदा स्तोतृभ्यो महि गोत्रा रुजासि । भूयिष्ठभाजो अध ते स्याम ।
This text occurs in Taittiriya Brāhmaṇam 3rd kāṇḍa, 7th prapāṭhaka, 11th anuvāka. It is only part of the original text.
ब्रह्म प्रावादिष्म तन्नो मा हासीत् ।
The above text including this short text, all of this also occurs again at the end of Taittiriya Aranyakam 4th prapāṭhaka, 42nd anuvāka.
It has the nature of a shānti mantra.
"O horse-equipped Indra (हरिव) who grows by our prayers, whatever deficiency is there in this ritual of ours, please remove it when you break up (रुजासि) the great clouds (महि गोत्रा) for the sake of the worshippers. Then by your grace, we will obtain great wealth.
We praise profusely the Brahman (i.e. the Paramātma as well as the Veda which talks about the Paramātma), may it never abandon us."