The chandas of the Bhaja Govindam song is पादाकुलकम् which comes under मात्राछन्दस् .
The metre (छन्दस्) of this song is moraic (मात्राछन्दस्). Maatraachandas is the meter according to quantities. Note that this is different from the meters like Anushtub that are based on syllables. In the syllable based meters, the arrangement is based on short (laghu “light”) or long (guru “heavy”) where in a syllable is metrically short only if it contains a short vowel and is not followed by consecutive consonants in the same pada; and all other syllables are long, by quality (having a long vowel or diphthong) or by position (being followed by a consonant cluster).
The maatra chandas is a meter in which it is not the number of syllables that determines the arrangement, but the sum of the syllabic quantities per verse (short = 1 quantity, long = 2 quantities).
There are 4 quarters (पाद:) in each shloka. Each paada has 16 maatraas in this Paadakulakam (पादाकुलकम्) variety under Maatraachandas. In total 16 quantities much occur and it does not matter at all how they are divided up.
The Maatra-chandas is rare in Sanskrit; but in modern Indian languages there is usually only this particular meter. Owing to the freer choice of melody, the performance comes much closer to singing than the other meters. This meter is especially suitable for being integrated into musical accompaniments and being accompanied by drums and other percussion instruments (due to the layaa aspect).
In Bhaja Govindam, apart from the first verse, all other verses have 16 mAtrAs (मात्रा), as per the description of the pAdakulakam variety of mAtrAsamaka (मात्रासमक) described in the work, vRttaratnAkara (वृत्तरत्नाकर) by Kedaarabhatta (केदारभट्ट).
Count 2 maatraas for long vowels (आ, ई, ऊ, ए, ऐ, ओ, औ) and short vowel+consonent (e.g., नम्)
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We can see here that the first verse does not completely fit in the chandas.