• vikhyāta-karmaṇām — of those of famous deeds
  Compound: vi + khyāta (widely known) + karman (deed). The Yadus' karmas are vikhyāta — broadcast. Vaiṣṇava karma is by definition broadcastable; secret virtue is incomplete (Caitanya-caritāmṛta: prema cannot be hidden).
• saṅkhyā — enumeration
  From sam + √khyā — to count. The verse confesses the impossibility of saṅkhyā. Same word as Sāṅkhya philosophy (enumeration of categories). Bhāgavatam admits: where Bhagavān multiplies, philosophy's count fails.
• yadu-vaṁśa-prasūtānām — of those born in the Yadu dynasty
  Triple compound: yadu + vaṁśa (lineage) + prasūta (brought forth). Birth in the Yadu line is itself an honor. Gauḍīya hagiography records that some Vaiṣṇava ācāryas were Yadus reincarnated — the line remains alive.
• ayutaiḥ — by ten thousands
  Instrumental plural of ayuta (10,000). Sanskrit's standard large number. The verse uses it to denote years that fail at counting — a deliberate poetic crashing of arithmetic at the threshold of Bhagavān's family.

• Whose fruits in my devotional history am I counting too narrowly?
• How does the uncountability of His blessings change my measuring habits?

Even ten thousand years could not count the great Yādavas. Bhāgavatam confesses its own enumerative limit: where Bhagavān resides, the proliferation of His associates exceeds any list. Aiśvarya's signature is uncountability.