It's not a will, but an administration bond. A bond is a promise to do something, against a penalty for default.
The widow Thamasina Leytie, supported by Pascoe Leytie (no relationship stated), is undertaking to administer the estate of her deceased husband in accordance with the law, against a penalty of 40 marks for any default.
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Noverint universi p(er) p(rese)ntes Nos Thamasina(m) Leytie p(ar)o(chie) de
Peranuthno in Com(itatu) Cornub(ie) vid(uam) et Pascatiu(m) Leytie
p(ar)o(chie) de Peran’ p(re)d(icto in Comitatu p(re)d(icto) Agricolam
teneri et firmit(er) obligari Will(el)mo Parker sacre theologie bacch(alar)io
Archinatus Cornubie Archi(diac)ono in quadraginta marcis bone et legalis
monete Anglie solvend(is) eidem Will(el)mo Parker aut suo c(er)to in hac p(arte)
attornato hered(ibus) Executor(ibus) administratoribus successoribus vel assignat(is)
suis. Ad quam quidem soluc(i)o(n)em bene et fidelit(er) faciend(am) obligam(us) no(s)
utri(us)q(ue) n(ost)ru(m) p(er) se p(ro) toto et in solido heredes executores et adm[inistratores]
n(ost)ros firmit(er) p(er) p(rese)ntes Sigillis n(ost)ris sigillat(us) Dat(um) xvo die
Decembris Anno Regni Dom(ini) n(ost)ri Jacobi dei grac(ia) Anglie Francie et
Hibernie reg(is) fidei defensor(is) &c decimo quinto et Scotie quinqua(-)
gesimo primo Annoq(ue) Domini 1617
May everyone know by these presents that we, Thamasina Leytie of the parish of Perranuthnoe in the county of Cornwall, widow, and Pascoe Leytie of the aforesaid parish of Peran’ in the aforesaid county, farmer, are held and firmly bound to William Parker, Bachelor of Sacred Theology, Archdeacon of the Archdeaconry of Cornwall, in (the sum of) forty marks of good and lawful money of England, to be paid to the same William Parker, or to his certain attorney in this matter, his heirs, executors, administrators, successors or assigns; for this payment well and faithfully to be made we bind ourselves, and each one of us for himself, for the whole and undivided (sum), and (we bind) our heirs, executors and administrators firmly by these presents; sealed with our seals; dated the 15th day of December in the fifteenth year of the reign of our lord James, by the grace of God King of England, France and Ireland, Defender of the Faith etc., and of Scotland the fifty-first, and in the year of the Lord 1617.